Tinea Infection
Common fungal skin infection. Also referred to as dermatophytosis or ringworm. Common areas affected include: head (tinea capitis), body (tinea corporis), groin ("jock itch"), feet ("athlete's foot").
Causative Agent(s): MANY! Common fungi include Trichophyton, Microsporum, and Epidermophyton.
S/S: Red, scaly, cracked skin. Ring-shaped rash, itchy skin, hair loss.
Transmission: Contact with contaminated animals, people, or personal items.
Dx: Clinical presentation. KOH prep of skin scraping confirms diagnosis.
Tx: Topical antifungal agents (e.g., clotrimazole), oral antifungal agents (e.g., fluconazole).
Prevention: Avoid sharing towels, combs, clothing. Avoid walking barefoot in locker rooms and public showers. Wash hands after playing with pets.
Smallpox
Serious infectious disease eradicated worldwide in 1980 due to vaccination.
Causative Agent(s): Variola virus.
S/S: High fever, body aches. Rash that starts in the mouth, then appears on the face, then spreads to the rest of the body. Pustules form, scab over, and leave scars.
Transmission: Respiratory droplets (e.g., coughing, sneezing), direct contact with sores or objects contaminated by sores.
Dx: Clinical presentation.
Tx: Supportive care, vaccination to lessen severity of disease (if given within 2 - 3 days of exposure), antivirals (e.g., brincidofovir).
Prevention: Smallpox vaccine. Not available to the general public as smallpox has been eradicated.
Hand, Foot, & Mouth Disease
Contagious viral infection common in children under 5 years old.
Causative Agent(s): Coxsackievirus.
S/S: Fever, painful mouth sores, skin rash on the palms of the hands and soles of the feet.
Transmission: Respiratory droplets (e.g., coughing, sneezing), close contact with an infected person, contact with contaminated objects.
Dx: Clinical presentation.
Tx: Supportive (e.g., acetaminophen, hydration).
Prevention: Hand hygiene, avoid contact with sick individuals, disinfect surfaces. Avoid touching eyes, nose, mouth.
Fifth Disease
Mild viral illness that is common in childhood. Also referred to as Erythema Infectiosum. TORCH infection.
Causative Agent(s): Parvovirus B19.
S/S: Fever, cough, headache, sore throat, red rash on face (i.e., "slapped cheek" rash), joint pain.
FIFTH: Think of FIVE fingers slapping the cheek.
Transmission: Respiratory droplets (e.g., coughing, sneezing).
Dx: Clinical presentation.
Tx: Supportive (e.g., acetaminophen, rest).
Prevention: Hand hygiene.
Roseola
Viral infection that commonly affects young children and infants. Also referred to as roseola infantum or sixth disease.
Causative Agent(s): Human herpesvirus-6 or human herpesvirus-7.
S/S: High fever, pink, rose-colored rash that starts on the trunk and spreads to the face and extremities.
Roseola causes a rose-colored rash.
Transmission: Respiratory droplets (e.g., coughing, sneezing).
Dx: Clinical presentation.
Tx: Supportive (e.g., acetaminophen, cool sponge baths).
Prevention: Hand hygiene.
Oral Herpes
Viral infection of the mouth that causes blisters known as cold sores or fever blisters.
Causative Agent(s): Herpes simplex virus type 1 (most common), herpes simplex virus type 2 (spread through oral-genital contact).
S/S: Asymptomatic. Painful blisters around mouth that break open and crust over. Flu-like symptoms (e.g., fever, body aches) and itching, burning, and tingling around the mouth may occur before sores appear.
Virus becomes dormant in body and can be reactivated by a trigger (e.g., stress).
Transmission: Personal contact with an infected individual (e.g., kissing), contact with a herpes sore or contaminated object (e.g., towel, razor).
Dx: Clinical presentation, laboratory analysis of blood sample or sample taken from sore.
Tx: No cure. Antiviral agents (e.g., acyclovir) to lessen severity and frequency of outbreaks.
Prevention: Avoid intimate contact and sharing of items with someone with a cold sore.
Papillomas
Common viral skin infection that causes benign skin growths. Commonly known as "warts".
Causative Agent(s): Human papillomavirus.
S/S: Vary in appearance. Common warts often occur on the hands and present as rough bumps with black "seeds". Plantar warts occur on the soles of the feet and are flat or grow inward.
Transmission: Direct contact with wart or contaminated item (e.g., towel).
Dx: Clinical presentation, skin biopsy.
Tx: Self-resolving, cantharidin, cryosurgery (i.e., freezing), excision (i.e. cutting out wart).
Prevention: Clean and cover cuts or scrapes, hand hygiene, prevent dry/cracked skin, don't bite nails. Wear shoes in locker rooms, pool areas, public showers.
Conjunctivitis
Inflammation or infection of the conjunctiva. Commonly known as "pink eye".
Causative Agent(s): MANY! Viruses (e.g., adenoviruses), bacteria (e.g., Haemophilus influenzae), allergens.
S/S: Pink/red color in the white of the eye(s), swelling of the conjunctiva, itching, irritation, burning, discharge, crusting of eyelids or eyelashes.
Transmission: Respiratory droplets, close personal contact with an infected person, touching eye after touching a contaminated object.
Dx: Clinical examination of eye and review of accompanying symptoms, laboratory testing of eye discharge.
Tx: Viral conjunctivitis is typically self-resolving, antibiotic eye drops for bacterial conjunctivitis.
Otitis Externa
Infection of the outer ear and ear canal. Commonly known as "swimmer's ear".
Causative Agent(s): Pseudomonas aeruginosa, Staphylococcus aureus.
S/S: Itching, redness, pain, pus draining from infected ear.
Transmission: Water trapped in the ear canal allows for growth of bacteria. Not contagious.
RF: Swimming, humidity.
Dx: Clinical examination with otoscopy.
Tx: Ear drops with an antibiotic and steroid (e.g., ciprofloxacin with hydrocortisone).
Prevention: Dry ears thoroughly after swimming or showering. Do not put objects in ear canal.
Necrotizing Fasciitis
Life-threatening, rapidly spreading bacterial infection that affects the fascia (i.e., connective tissue between the skin and muscle), leading to tissue death. Known as "flesh-eating disease".
Causative Agent(s): Streptococcus pyogenes (i.e., Group A Streptococcus). Staphylococcus aureus, Vibrio vulnificus, Aeromonas hydrophila.
S/S: Early symptoms include redness, warmth, swelling, severe pain, fever. Later symptoms include ulcers, blisters, and changes in the color of the skin.
Transmission: Bacteria enters via a break in the skin (e.g., cut, burn, surgical wound) in most cases.
Dx: Tissue biopsy.
Tx: Debridement (i.e., removal of dead/infected tissue), amputation, IV antibiotics.
Impetigo
Highly contagious bacterial skin infection.
Causative Agent(s): Staphylococcus aureus, Streptococcus pyogenes.
S/S: Pustules and vesicles around the mouth and nose that rupture and form a "honey-colored" crust.
Transmission: Direct contact with infected individuals or drainage from lesions.
RF: Children (2 - 5 yrs. old), poor personal hygiene, warm/ humid conditions.
Dx: Clinical presentation.
Tx: Topical antibiotics (e.g., mupirocin), oral antibiotics (e.g., cephalexin).
Folliculitis
Superficial bacterial skin infection. Can lead to furuncles or carbuncles, which are deeper infections that may cause systemic symptoms (e.g., fever).
Causative Agent(s): Staphylococcus aureus.
S/S: Itchy, red, pus-filled bumps.
Transmission: Usually not contagious.
RF: Sweat, skin injuries, ingrown hairs, tight clothing, irritation from shaving.
Dx: Clinical presentation.
Tx: Self-resolving, topical antibiotics. Furuncles or carbuncles may require drainage and treatment with systemic antibiotics.
Acne
Common skin condition that occurs when hair follicles become clogged with sebum and dead skin cells.
Causative Agent(s): Cutibacterium acnes (previously named Propionibacterium acnes).
I don't look like a cutie because of Cutibacterium.
S/S: Closed comedones (i.e., whiteheads), open comedones (i.e., blackheads), papules, pustules, nodules.
Transmission: Not contagious.
RF: Teenagers and young adults due to hormonal changes that cause ↑ sebum production.
Dx: Clinical presentation.
Tx: Topical agents (e.g., salicylic acid, retinoids, benzoyl peroxide), oral medications (e.g., antibiotics, isotretinoin).
Trichomoniasis
Sexually transmitted infection caused by a protozoan parasite. Referred to as "trich".
Causative Agent(s): Trichomonas vaginalis.
S/S: Asymptomatic in most people. Genital itching or burning, discomfort when urinating, vaginal or penile discharge.
Infection ↑ risk of acquiring HIV and is associated with pregnancy complications (e.g., preterm birth).
Transmission: Sexual contact.
Dx: Wet mount microscopy using vaginal, urethral, endocervical, or urine sample.
Tx: Antiprotozoal agent (e.g., metronidazole).
Prevention: Safe sexual practices.
Vaginal Candidiasis
Fungal infection caused by overgrowth of candida. Commonly known as a "yeast infection".
Causative Agent(s): Candida spp. (usually Candida albicans).
S/S: Vaginal itching, discomfort, burning, thick/white discharge that resembles cottage cheese.
Transmission: Not usually transmitted to others, but can be transmitted with sexual contact.
RF: Use of antibiotics, birth control pills, pregnancy, diabetes mellitus, immunosuppression.
Dx: Clinical presentation, microscopic examination of vaginal secretions.
Tx: Topical or oral antifungals (e.g., fluconazole).
Prevention: Wear cotton underwear, do not douche, avoid scented feminine products.
Card 16
Human Papillomavirus (HPV)
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Prevention
Answer
Human Papillomavirus (HPV)
Most common sexually transmitted infection, which may lead to the development of genital warts and cancer.
Causative Agent(s): Human papillomavirus.
S/S: Asymptomatic. Small bumps in genital area.
HPV is the primary risk factor for cervical cancer.
Transmission: Sexual contact.
Dx: Pap test using a sample of cervical cells.
Tx: No cure. Medication or surgery to remove warts.
Prevention: HPV vaccine (e.g., Gardasil), safe sexual practices.
Genital Herpes
Sexually transmitted disease that causes genital lesions. TORCH infection.
Causative Agent(s): Herpes simplex virus type 2 (most common), herpes simplex virus type 1 (spread through oral-genital contact).
S/S: Asymptomatic. Painful blisters on genitals that burst and crust over. Flu-like symptoms (e.g., fever, body aches) may occur before the appearance of blisters during the first outbreak.
May cause repeat outbreaks over time as the virus can be reactivated during times of stress, fatigue, or illness.
Transmission: Direct contact (e.g., oral or sexual contact). Can be transmitted during childbirth, causing neonatal herpes.
Dx: Clinical presentation, viral culture of sample from lesion, serological tests to identify antibodies to HSV.
Tx: No cure. Antiviral agents (e.g., acyclovir) to ↓ severity and frequency of outbreaks.
Prevention: Safe sexual practices.
Chlamydia
Most commonly reported sexually transmitted infection in the U.S.
Causative Agent(s): Chlamydia trachomatis.
S/S: Often asymptomatic. Painful urination, abnormal vaginal discharge, discharge from the penis.
Transmission: Sexual contact, childbirth via infected mother.
Dx: Vaginal swab, urine sample.
Tx: Antibiotics (e.g., azithromycin).
Untreated chlamydia can lead to pelvic inflammatory disease, infertility, and/or ectopic pregnancy in women. Chlamydia during pregnancy can be transmitted to the infant during delivery, causing serious infections.
Prevention: Safe sexual practices (e.g., condoms), abstinence.
Gonorrhea
Common sexually transmitted infection.
Causative Agent(s): Neisseria gonorrhoeae.
S/S: Often asymptomatic. Painful urination, increased vaginal discharge, vaginal bleeding between periods, purulent discharge from penis.
Transmission: Sexual contact, childbirth via infected mother.
Dx: Urine sample, swab specimens of throat, genitals, and/or rectum.
Tx: Antibiotics (e.g., ceftriaxone).
Untreated gonorrhea can lead to pelvic inflammatory disease and infertility. Gonorrhea during pregnancy can be transmitted to the infant during delivery, causing serious infections.
Prevention: Safe sexual practices (e.g., condoms), abstinence.
Bacterial Vaginosis (BV)
Imbalance in the normal vaginal microbiome.
Causative Agent(s): Gardnerella vaginalis. Decline in Lactobacilli and ↑ vaginal pH allows for overgrowth of G. vaginalis.
S/S: Vaginal discharge with a fishy odor. Itching, pain, burning in vagina. Many individuals are asymptomatic.
Transmission: Unclear. Not a sexually transmitted infection, but more common in sexually active individuals.
RF: Douching, multiple sexual partners, recent antibiotic use.
Dx: Microscopic examination and pH testing of vaginal fluid sample.
Tx: Antibiotics (e.g., metronidazole).
Prevention: Avoid douching, safe sexual practices.
Untreated bacterial vaginosis increases risk of STIs and pregnancy complications.
Taeniasis
Parasitic infection caused by ingestion of tapeworm larvae, which hatch and mature inside the intestines.
Causative Agent(s): Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm).
S/S: No symptoms. Abdominal pain, loss of appetite, weight loss, passing of eggs or gravid proglottids (i.e., tapeworm segments filled with eggs) in the feces.
Transmission: Ingestion of raw/undercooked beef or pork infected with tapeworm larvae.
Dx: Microscopic examination of three stool samples (collected on different days) for presence of tapeworm eggs.
Tx: Antihelminthic agent (e.g., Praziquantel).
Prevention: Cook meat to a safe temperature. Good hygiene and sanitation practices.
Enterobiasis
Helminthic infection caused by a roundworm that colonizes the colon of humans. Also known as pinworm.
Causative Agent(s): Enterobius vermicularis.
S/S: Itching around the anus and difficulty sleeping (due to female pinworms leaving the intestine through the anus to lay eggs on the perianal skin while the infected individual sleeps).
Transmission: Ingestion of larvae (e.g., eating after touching something contaminated).
Dx: Tape test. Tape is applied to the anus first thing in the morning and microscopically observed for worms and eggs.
Tx: Antihelminthic medication (e.g., albendazole).
Prevention: Hand hygiene, daily bathing and changing of underclothes, frequent laundering of clothes and linens.
Cryptosporidiosis
Parasitic intestinal infection known as "Crypto".
Causative Agent(s): Cryptosporidium parvum, Cryptosporidium hominis.
S/S: Watery diarrhea, stomach cramps, nausea, vomiting, fever, dehydration, weight loss.
Transmission: Ingestion of water or food contaminated with the feces of people or animals infected with Crypto.
Cryptosporidium survives chlorination.
RF: Swallowing recreational water (e.g., swimming pool, lake, river), oral-anal sexual contact.
Dx: Examination of stool samples over three different days.
Tx: Supportive care (e.g., hydration), antiprotozoal agent (e.g., nitazoxanide).
Prevention: Hand hygiene, do not swallow swimming water, safe sexual practices.
Giardiasis
Diarrheal disease caused by a parasite. Most common protozoan infection in the world.
Causative Agent(s): Giardia duodenalis (G. lamblia).
S/S: Diarrhea, gas, greasy/malodorous stool, stomach cramps, nausea.
Transmission: Ingestion of water or food contaminated with the feces of people or animals infected with Giardia.
Giardia survives chlorination.
RF: Childcare settings, travel to areas with poor sanitation.
Dx: Microscopic examination of stool sample for ova and parasite.
Tx: Oral rehydration, antiprotozoal agent (e.g., metronidazole).
Prevention: Hand hygiene, avoid drinking contaminated water.
Giardiasis is also called 'Beaver Fever', as beavers are a reservoir for Giardia.
Viral Hepatitis
Infection causing liver inflammation and damage. Hepatitis B is a TORCH infection.
Causative Agent(s): Hepatitis viruses A, B, C, D, E.
S/S: Fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine, clay-colored stool, joint pain, jaundice.
Transmission: Fecal-oral route for Hep A and E (e.g., contaminated food/water, close contact with infected person). Contact with infected blood or body fluids for Hep B, C, D (e.g., sexual contact, IV drug use).
Hep D can only occur in individuals already infected with Hep B.
Diagnosis: Serological testing for virus-specific antibodies or antigens.
Treatment: Supportive care (e.g., rest, fluids) for Hep A, acute Hep B, and Hep E. Antivirals, interferons for chronic Hep B and C. Interferons for Hep D.
Prevention: Hep A and Hep B vaccine. Hand hygiene to prevent Hep A. Safe sexual practices, no sharing syringes/needles to prevent Hep B, C, D.
Clostridioides difficile Infection
Gastrointestinal illness caused by disruption of the normal microbiota with antibiotic use. Previously known as Clostridium difficile.
Causative Agent(s): Clostridioides difficile (i.e., C. diff).
S/S: Watery diarrhea, fever, stomach pain, loss of appetite, nausea.
Transmission: Overgrowth of C. diff in normal microbiota due to antibiotic use. Spread through food or objects contaminated with feces of an infected person.
Dx: Laboratory analysis of stool sample.
Tx: Discontinue previous antibiotic and initiate new antibiotic (e.g., vancomycin), fecal transplantation.
Prevention: Prevent spread through isolation of infected person, hand hygiene, disinfection of surfaces. Use antibiotics appropriately.
Clostridium perfringens Gastroenteritis
Mild foodborne illness associated with foods kept at an unsafe temperature.
Causative Agent(s): Toxin produced by Clostridium perfringens, a bacteria commonly found in raw meat and poultry.
S/S: Stomach pain, watery (non-bloody) diarrhea, vomiting.
Transmission: Ingestion of contaminated food.
Outbreaks tend to happen in places that serve large groups of people (e.g., nursing homes) and are linked to foods served during the holidays (e.g., turkey, roast beef).
Dx: Detection of bacteria or toxin in stool or food linked to illness.
Tx: Supportive care (e.g., extra fluids).
Prevention: Cook foods to safe temperature, refrigerate leftovers within 2 hours.
Peptic Ulcer Disease (PUD)
Erosion in the lining of the gastrointestinal tract.
Causative Agent(s): Helicobacter pylori, responsible for 90% of duodenal ulcers and 70-90% of gastric ulcers.
S/S: Abdominal pain, bloating, nausea, vomiting, weight loss, blood in vomit or stool.
Transmission: Fecal-oral route via contaminated food/water. Contact with an infected person's saliva or body fluids.
Dx: Blood, breath, or stool test to check for H. pylori. Upper endoscopy with biopsy.
Tx: Multiple antibiotics, proton pump inhibitor.
Prevention: Hand hygiene, avoid contaminated food/water.
Campylobacteriosis
Most common bacterial cause of diarrhea in the United States.
Causative Agent(s): Campylobacter jejuni.
S/S: Diarrhea (often bloody), stomach cramps, nausea, vomiting, fever, fatigue.
Transmission: Consumption of contaminated food, especially raw/undercooked poultry. Handling of infected animal feces.
I went to camp to have fun, but came home with diarrhea due to campylobacteriosis.
Dx: Stool culture.
Tx: Usually self-limiting. Supportive care (e.g., extra fluids). Antibiotics for individuals with severe infection or weakened immune system.
Prevention: Safe food preparation and proper hand hygiene.
Cholera
Acute diarrheal illness associated with poor sanitation.
Causative Agent(s): Vibrio cholerae.
S/S: Profuse watery diarrhea (i.e., "rice water" stools), vomiting, leg cramps.
Transmission: Fecal-oral route via contaminated food/water, consumption of raw/undercooked shellfish (V. cholerae naturally inhabits coastal salt water environments and can concentrate inside shellfish).
Dx: Stool culture.
Tx: Rehydration (e.g., oral rehydration solution), antibiotics (e.g., doxycycline), zinc (for children).
Prevention: Drink and use safe water, hand hygiene, use toilets (or safe sanitation facility), safe food preparation.
Card 33
Diarrheagenic E. coli
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Prevention
Answer
Diarrheagenic E. coli
Diarrheal illness caused by a pathogenic strain of E. coli.
Causative Agent(s): Shiga-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC).
S/S: Watery or blood diarrhea, abdominal cramping, vomiting.
Transmission: Food or water contaminated with human or animal feces.
Dx: Stool culture.
Tx: Supportive care (e.g., hydration), antidiarrheal agent (e.g., loperamide), antibiotics (e.g., fluoroquinolones).
Antibiotics are not recommended for STEC due to risk for hemolytic uremic syndrome.
Prevention: Hand hygiene, safe food handling (e.g., avoid cross contamination), cook meats thoroughly, avoid unpasteurized milk and juice.
Typhoid Fever
Serious bacterial illness, most common in parts of the world with poor sanitation and hygiene.
Causative Agent(s): Salmonella typhi, Salmonella paratyphi.
S/S: High fever, abdominal pain, severe diarrhea, rash.
Transmission: Consumption of contaminated food or drinks.
Some people can be asymptomatic carriers of S. typhi, continuing to shed the bacteria in their stool and spread the disease (e.g., "Typhoid Mary").
Dx: Blood, stool, urine, or bone marrow culture.
Tx: Antibiotics (e.g., azithromycin).
Prevention: Vaccination prior to traveling to high-risk areas, safe eating/drinking habits.
Salmonellosis
Common bacterial gastrointestinal illness.
Causative Agent(s): Salmonella enterica, Salmonella bongori.
S/S: High fever, diarrhea, stomach cramps, nausea, vomiting, headache.
Transmission: Consumption of contaminated foods (e.g., raw poultry, meat, dairy products), contact with feces of an animal that harbors Salmonella (e.g., reptile).
Dx: Detection of Salmonella in stool sample or body fluids.
Tx: Supportive care (e.g., extra fluids), antibiotics for severe cases.
Prevention: Wash hands/surfaces often, safe food handling, cook foods to safe temperature, refrigerate foods properly.
Shigellosis
Bacterial infection affecting the lining of the intestines. Also known as bacillary dysentery.
Causative Agent(s): Shigella sonnei, Shigella flexneri.
S/S: Abdominal pain/cramping, fever, nausea, vomiting, watery/bloody diarrhea. Blood, mucus, or pus in stool.
Transmission: Fecal-oral route (e.g., touching mouth after touching contaminated surface or fecal matter), consumption of contaminated food/water.
Dx: Lab identification of Shigella in stool.
Tx: Fluid and electrolyte replacement, antibiotics for severe cases (e.g., ciprofloxacin).
Prevention: Hand hygiene, proper disposal of diapers, disinfect diaper changing area after use.
Staphylococcal Food Poisoning
Food poisoning caused by ingestion of contaminated food.
Causative Agent(s): Enterotoxin produced by Staphylococcus aureus.
S/S: Nausea, vomiting, diarrhea, dehydration.
Transmission: Ingestion of foods contaminated with S. aureus toxin.
Bacteria are killed with cooking, but toxins are not destroyed.
Dx: Identification of toxin in food sample or biological sample (e.g., stool, vomit).
Tx: Self-resolving, supportive care (e.g., rehydration).
Prevention: Hand hygiene, proper storage and preparation of food.
Mumps
Contagious, preventable viral illness.
Causative Agent(s): Mumps virus.
S/S: Parotitis (i.e., swelling of salivary glands), fever, tiredness, headache, loss of appetite. May be asymptomatic.
Complications of mumps include infertility in males, deafness, meningitis, and encephalitis.
Transmission: Contact with saliva or respiratory droplets (e.g., coughing, sneezing).
Dx: Virus culture and antibody testing using urine, blood, cerebrospinal fluid, or respiratory secretion sample.
Tx: Usually self-limiting, supportive care (e.g., warm/cold compresses for parotid swelling).
Prevention: MMR vaccine.
Dental Caries
Tooth decay that occurs when bacterial biofilms develop on the teeth, and acids produced by the bacteria dissolve the enamel.
Causative Agent(s): Most commonly Streptococcus mutans.
S/S: Asymptomatic with early tooth decay. Tooth pain, sensitivity to hot/cold, area of discoloration on tooth, hole in tooth, soft/sticky area on tooth.
Transmission: Not transmissible, caused by bacteria in the normal oral microbiota.
Dx: Clinical signs/symptoms, x-ray.
Tx: Fluoride (early stages), removal of decayed tooth tissue and placement of a filling.
Prevention: Get enough fluoride (e.g., toothpaste, drinking water), brush and floss teeth, limit sugary foods/drinks, regular checkups with dentist.
Primary Amoebic Meningoencephalitis (PAM)
Rare, deadly brain infection caused by an amoeba.
Causative Agent(s): Naegleria fowleri.
S/S: Headache, fever, nausea, vomiting, stiff neck, confusion, loss of balance, seizures, hallucinations, death in 3 - 7 days.
Transmission: In most cases, amoeba enters nose while swimming in warm freshwater and travels to the brain. Use of household tap water to irrigate sinuses.
Dx: Analysis of cerebrospinal fluid obtained via lumbar puncture.
Tx: Optimal treatment is unknown. Combination of drugs recommended (e.g., amphotericin B, fluconazole, azithromycin).
Prevention: Avoid water activities in warm freshwater, hold nose shut or use nose clips. Use safe water for sinus irrigation.
African Trypanosomiasis
Parasitic infection transmitted by a fly found in rural Africa. Also known as "sleeping sickness".
Causative Agent(s): Trypanosoma brucei rhodesiense (East African trypanosomiasis), Trypanosoma brucei gambiense (West African trypanosomiasis).
S/S: Fever, headache, swollen lymph nodes, muscle/joint aches, insomnia during the night, sleepiness during the day, chancre (i.e., painful, red sore) at site of fly bite.
Transmission: Bite from a tsetse fly.
Dx: Microscopic detection of parasite in blood, lymph, cerebrospinal fluid, or skin biopsy of chancre.
Tx: Antimicrobial agents (e.g., pentamidine, fexinidazole, suramin).
Prevention: Minimize contact with tsetse fly, insect control measures.
Transmissible Spongiform Encephalopathies (TSEs)
Extremely rare, degenerative, fatal neurological diseases caused by prions (e.g., Creutzfeldt-Jakob disease, kuru).
Causative Agent(s): Prions.
Prions are acellular pathogenic agents that cause normal protein found in the brain (PrPC) to misfold into a denatured form (PrPSc).
S/S: Personality changes, unsteady gait, insomnia, confusion, coma, death.
Transmission: Ingestion of infected nervous system tissue, tissue transplants. Inherited with familial CJD (i.e., genetic disease, not an infectious disease).
Dx: Examination of brain tissue after death.
Tx: No treatment, supportive care.
Poliomyelitis
Highly contagious viral disease that can cause paralysis.
Causative Agent(s): Poliovirus.
S/S: Flu-like symptoms (e.g., sore throat, fever, nausea, headache), meningitis, paralysis.
Many individuals are asymptomatic or only have flu-like symptoms. 1 in 200 cases cause paralysis.
Transmission: Fecal-oral route, respiratory droplets.
Dx: Analysis of stool, blood, urine, spinal fluid, or throat swab samples.
Tx: No cure, supportive care.
Prevention: Inactivated poliovirus vaccine (IPV) in U.S., oral poliovirus vaccine (OPV) in other parts of the world.
Rabies
Rare, deadly zoonotic disease.
Causative Agent(s): Rabies virus.
S/S: Weakness, fever, headache, confusion, seizures, hallucinations, hydrophobia (i.e., fear of water).
Transmission: Bite or scratch from an infected animal.
Dx: Laboratory examination of blood, saliva, spinal fluid, or skin biopsy specimens.
Tx: Post-exposure prophylaxis (i.e., immune globulin, rabies vaccine), wound cleansing.
Prevention: Rabies vaccine for at risk individuals (e.g., veterinarians).
There is no cure for rabies once clinical signs become evident. Even with appropriate treatment, rabies is >99% fatal.
Zika
Mosquito-borne viral infection. TORCH infection.
Causative Agent(s): Zika virus.
S/S: Fever, rash, headache, joint pain, red eyes, muscle pain. Fetal infections can result in severe brain defects (e.g., microcephaly).
Transmission: Bite from an infected Aedes species mosquito, sexual contact. Can be transmitted during pregnancy to the developing fetus, causing birth defects.
Dx: Clinical symptoms, blood or urine test to test to confirm presence of Zika infection.
Tx: Supportive (e.g., rest, fluids, acetaminophen).
Prevention: Insect repellent, mosquito control, safe sexual practices.
Arboviral Encephalitis
Inflammation of the brain caused by an insect-borne virus (e.g., eastern equine encephalitis, western equine encephalitis, St. Louis encephalitis, West Nile encephalitis).
Causative Agent(s): Arboviruses.
S/S: Fever, headache, altered mental status, seizures, nausea, vomiting.
Transmission: Bite from a blood-sucking arthropod (e.g., mosquito, tick).
Dx: Analysis of cerebrospinal fluid or blood for virus or virus-specific antibodies.
Tx: Supportive (i.e., symptom management).
Prevention: Insect repellant, mosquito nets. Eliminate stagnant water.
Hansen's Disease (Leprosy)
Chronic infectious disease that causes skin lesions and nerve damage. Very rare in the United States.
Causative Agent(s): Mycobacterium leprae.
S/S: Numb, discolored patches of skin. Muscle weakness or paralysis in hands/feet, thick/stiff skin, painless ulcers on soles of the feet.
Transmission: Respiratory droplets, prolonged contact (i.e., several months) with someone with untreated leprosy. Contact with a nine-banded armadillo, a natural host and reservoir for M. leprae.
Incubation period may be up to 20 years.
Dx: Clinical presentation, skin and/or nerve biopsy.
Tx: Multidrug therapy (2 - 3 antibiotics).
Listeriosis
Bacterial foodborne illness that more commonly causes illness in pregnant people and newborns, older individuals, and immunocompromised individuals.
Causative Agent(s): Listeria monocytogenes.
S/S: Fever, muscle aches, fatigue, headache, stiff neck, confusion, miscarriage in pregnant women.
Transmission: Consuming foods contaminated with L. monocytogenes.
Dx: Culture of blood, spinal fluid, or amniotic fluid.
Tx: Antibiotics (e.g., ampicillin).
Prevention: Safe food handling, cook meats thoroughly. Avoid unpasteurized dairy products and raw sprouts.
Unlike most bacteria, Listeria monocytogenes will continue to grow even at refrigeration temperatures.
Schistosomiasis
Disease caused by blood flukes (i.e., parasitic worms). Also known as bilharzia.
Causative Agent(s): Schistosoma spp. (e.g., S. mansoni, S. haematobium, S. japonicum).
S/S: Early signs include rash and itchy skin. Fever, chills, cough, and muscle aches develop 1 - 2 months later. Intestine, liver, and bladder damage occurs years after infection.
Transmission: Contact with contaminated freshwater (e.g., swimming, bathing, washing).
Dx: Urine and stool samples to test for presence of parasites.
Tx: Antiparasitic agent (e.g., Praziquantel).
Prevention: Avoid swimming in freshwater where schistosomiasis occurs (e.g., southern and sub-Saharan Africa), drink safe water.
Toxoplasmosis
Infection caused by a parasite. TORCH infection.
Causative Agent(s): Toxoplasma gondii. Cats are hosts for the parasite, immature eggs are shed in cat feces.
S/S: Usually asymptomatic. Flu-like symptoms (e.g., swollen lymph nodes) or severe symptoms in immunocompromised individuals (e.g., ocular infections, encephalitis). Premature birth, congenital defects in infants.
Transmission: Ingestion of contaminated food or water, contact with cat feces (e.g., changing litter), mother-to-child transmission during pregnancy.
Dx: Serologic testing to check for antibodies to T. gondii. TORCH screening during pregnancy.
Tx: Not necessary for most people. Antiprotozoal agents, antibiotics for immunocompromised and pregnant individuals.
Prevention: Cook meat thoroughly, avoid drinking untreated water. Pregnant or immunocompromised individuals should avoid changing cat litter.
Malaria
Mosquito-borne disease caused by a parasite.
Causative Agent(s): Plasmodium spp. (e.g., P. falciparum, P. vivax, P. ovale, P. malariae).
S/S: Fever, chills, headache, nausea, vomiting. Left untreated, can lead to kidney failure, seizures, confusion, coma.
Transmission: Bite from an infected Anopheles mosquito.
Dx: Microscopic identification of Plasmodium in blood sample.
Tx: Antimalarial agent (e.g., chloroquine).
Prevention: Mosquito control, use of nets to reduce contact, antimalarial prophylaxis for travelers.
Ebola Disease
Deadly disease caused by an ebolavirus, occurring primarily on the African continent.
Causative Agent(s): Zaire, Sudan, Taï Forest, and Bundibugyo ebolaviruses.
S/S: Fever, severe headache, muscle/joint pain, sore throat, abdominal pain, diarrhea, vomiting, hemorrhaging.
Transmission: Contact with blood or body fluids from an infected person, contact with contaminated objects.
Dx: Detection of virus or antibodies in blood sample.
Tx: Monoclonal antibodies, supportive care (e.g., fluids, pain management), isolation to prevent spread.
Prevention: Ebola vaccine for high-risk individuals (e.g., healthcare workers at Ebola treatment centers).
Dengue Fever
Viral infection transmitted via mosquito bite in tropical and subtropical regions worldwide.
Causative Agent(s): Flavivirus (dengue virus 1, 2, 3, or 4).
S/S: Many infections are asymptomatic. Nausea, vomiting, aches/pains, positive tourniquet test, ↓ WBCs. Serious infections cause respiratory distress, severe bleeding, and severe organ impairment.
Transmission: Bite from an infected Aedes species mosquito.
Dx: Detection of virus or antibodies in blood sample.
Tx: Supportive (e.g., acetaminophen, rest, fluids).
Prevention: Mosquito control, dengue vaccine in areas where dengue is endemic.
Cytomegalovirus Disease
Viral illness that causes more severe symptoms in immunocompromised individuals. TORCH infection.
Causative Agent(s): Cytomegalovirus (CMV).
S/S: Fever, sore throat, fatigue in healthy people. In neonates: brain, liver, spleen, lung, hearing, and growth problems. In immunocompromised: eye, lung, liver, GI problems.
Transmission: Direct contact with bodily fluids (e.g., saliva, urine).
Dx: Adults: Blood test to detect CMV antibodies. Newborns: PCR test of urine or saliva sample.
Tx: Self-resolving for most people. Antivirals, antibody therapy for immunocompromised individuals.
Infectious Mononucleosis
Contagious viral infection, more common in teens and young adults. Often referred to as "mono" or "kissing disease".
Causative Agent(s): Epstein-Barr virus.
S/S: Fever, sore throat, swollen lymph nodes in the neck, fatigue, enlarged spleen, rash.
Transmission: Bodily fluids (e.g., saliva), contaminated objects (e.g., drinking glass, toothbrush).
Dx: Blood test to check for antibodies (e.g., monospot test).
Tx: Symptom relief (e.g., hydration, rest, over-the-counter pain relievers).
Rocky Mountain Spotted Fever
Potentially deadly tickborne disease.
Causative Agent(s): Rickettsia rickettsii.
S/S: Fever, headache, nausea, vomiting, body aches, rash (i.e., red splotches or pinpoint dots).
Transmission: Bite from tick (e.g., American dog tick, Rocky Mountain wood tick, brown dog tick).
Dx: Clinical signs/symptoms and recent tick bite or exposure to areas with ticks, serological tests to check for antibodies.
Tx: Antibiotics (e.g., doxycycline).
Prevention: Insect repellant, protective clothing, remove ticks promptly.
Cat Scratch Disease
Bacterial infection spread by cats.
Causative Agent(s): Bartonella henselae. Cats get infected with B. henselae from flea bites or infected flea dirt.
S/S: Red, swollen lesion at the site of the bite/scratch, swollen lymph nodes near the site of the bite/scratch, fever, headache, poor appetite.
Transmission: Bite or scratch from an infected cat, or an infected cat licking a person's open wound.
Dx: Bacteria are difficult to culture. Clinical examination, serological tests to check for antibodies to B. henselae.
Tx: Usually self-resolving, antibiotics for immunocompromised individuals.
Prevention: Wash cat bites/scratches right away with soap and running water.
Brucellosis
Zoonotic bacterial infection. Known by many other names, such as "remitting fever", "undulant fever", and "Mediterranean fever".
Causative Agent(s): Brucella melitensis (from sheep), Brucella suis (from pigs), Brucella abortus (from cattle), Brucella canis (from dogs).
Brucella is easily aerosolized and is a potential biological weapon.
S/S: Fluctuating fever that spikes every afternoon, sweating, headache, joint/muscle pain, fatigue.
Transmission: Contact with infected animals or contaminated dairy products.
Dx: Blood and bone marrow cultures. Serological tests to check for antibodies to bacteria.
Tx: Multi-drug antibiotic therapy (e.g., doxycycline and rifampin).
Prevention: Do not consume raw meat or unpasteurized dairy products. Wear protective equipment when handling animal tissue. Vaccination for animals.
Anthrax
Rare, serious bacterial disease. Cutaneous anthrax is most common.
Causative Agent(s): Bacillus anthracis.
B. anthracis is a potential agent of bioterrorism.
S/S:
- Cutaneous Anthrax: Skin ulcer with black eschar (i.e., dead skin tissue).
- Inhalation Anthrax: High fever, shortness of breath, cough, chest pain.
- Gastrointestinal Anthrax: Fever, sore throat, bloody vomiting, diarrhea.
Transmission: Inhalation of spores, ingestion of food/water contaminated with endospores, contact with endospores in the soil.
RF: Contact with infected animals or animal products.
Dx: Testing for antibodies or toxins in blood.
Tx: Antibiotics (e.g., ciprofloxacin), antitoxin therapy.
Prevention: Vaccine for high-risk individuals.
Leptospirosis
Most common zoonotic disease in the world. Also known as Weil's disease.
Causative Agent(s): Leptospira spp.
S/S:
- First phase: Flu-like symptoms (e.g., fever, chills, headache, muscle aches, vomiting, diarrhea).
- Second phase (i.e., Weil's disease): Fever, kidney failure, liver failure, and/or meningitis.
Transmission: Exposure to the urine of an infected animal, through direct contact or contact with soil or water contaminated by the urine.
Dx: Serological testing to detect antibodies to Leptospira spp.
Tx: Antibiotics (e.g., doxycycline).
Prevention: Avoid contact with infected animals and contaminated water or soil (e.g., avoid swimming in water contaminated with animal urine).
Cysticercosis & Neurocysticercosis
Parasitic infection caused by the ingestion of pork tapeworm eggs, resulting in the formation of cysts in the body.
Cysticercosis occurs when hatched larvae spread to the muscles or eyes. Neurocysticercosis occurs when hatched larvae invade the brain and spinal cord.
Causative Agent(s): Taenia solium (pork tapeworm).
S/S:
- Cysticercosis: Lumps under the skin, eye pain, double vision, vision loss, bulging eyes.
- Neurocysticercosis: Seizures/epilepsy, headache, cognitive issues.
Transmission: Ingestion of tapeworm eggs via fecal-oral route (e.g., contaminated food and water).
Dx: Imaging of the central nervous system (e.g., CT brain scan, MRI), serological testing.
Tx: Anthelmintic agents (e.g., albendazole), corticosteroids.
Prevention: Safe food handling, hand hygiene.
Botulism
Rare, potentially fatal illness caused by a toxin that attacks the body's nerves.
Causative Agent(s): Botulinum neurotoxin, produced by Clostridium botulinum.
S/S: Difficulty swallowing, muscle weakness, double/blurry vision, drooping eyelids, difficulty breathing. Nausea/vomiting, stomach pain, diarrhea with foodborne botulism.
Transmission:
- Foodborne Botulism: Ingestion of foods contaminated with botulinum toxin (e.g., homemade canned food).
- Wound Botulism: Contamination of wounds with C. botulinum endospores.
- Infant Botulism: Ingestion of foods contaminated with C. botulinum endospores (e.g., honey).
- Iatrogenic Botulism: Excess injection of C. botulinum for cosmetic or medical purposes.
Dx: Analysis of blood or stool sample for toxin.
Tx: Botulinum antitoxin.
Prevention: Proper home canning methods, do not feed honey to children
Meningitis
Inflammation of the meninges (i.e., membranes surrounding the brain and spinal cord).
Causative Agent(s): MANY! Most common causes:
- Bacteria: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae.
- Viruses: Enteroviruses, herpesviruses, arboviruses.
- Fungi: Cryptococcus neoformans.
S/S: Fever, neck pain/stiffness, photophobia (i.e., light sensitivity), headache, nausea and vomiting, confusion.
Transmission: Depends on causative agent (e.g., respiratory droplets, inhalation of fungal spores).
Dx: Cerebrospinal fluid culture and analysis.
Tx: Antibiotics for bacterial meningitis, antiviral agents for viral meningitis.
Prevention: Meningococcal, pneumococcal, Hib vaccines. Influenza, mumps, measles, chickenpox vaccines.
Card 68
American Trypanosomiasis
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Prevention
Answer
American Trypanosomiasis
Parasitic infection transmitted via insect vectors. Also referred to as Chagas disease.
Causative Agent(s): Trypanosoma cruzi.
S/S:
- Acute Phase: Fever, fatigue, body aches, vomiting, diarrhea, chagoma (i.e., swelling at infection site), Romaña's sign (i.e., eyelid swelling), enlargement of the liver or spleen.
- Chronic Phase: Heart issues (e.g., heart failure), GI issues (e.g., enlarged colon and esophagus).
Transmission: Bite from an infected Triatoma bug (i.e., "kissing bug").
Dx: Microscopic identification of parasite in blood sample.
Tx: Antiparasitic agents (e.g., benznidazole).
Prevention: Insect control measures (e.g., insecticides).
Card 69
Human Immunodeficiency Virus (HIV) Infection
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Prevention
Answer
HIV Infection
Viral infection that attacks the body's immune system, specifically CD4 cells. Left untreated, HIV leads to acquired immunodeficiency syndrome (AIDS). TORCH infection.
Causative Agent(s): Human immunodeficiency virus.
S/S:
- Stage 1: Flu-like symptoms (e.g., fever, swollen lymph nodes, muscle aches).
- Stage 2: Asymptomatic HIV infection.
- Stage 3: AIDS, causing serious, opportunistic infections (e.g., pneumonia, tuberculosis).
Transmission: Sexual contact. Sharing of needles, syringes, or other drug injection equipment. Transmission during pregnancy, birth, or breastfeeding.
Dx: Serological tests to check for presence of antibodies in blood sample.
Tx: No cure. Antiretroviral therapy (i.e., combination of many drugs to target different stages of the viral life cycle) to reduce viral load.
Prevention: Safe sexual practices (e.g., abstinence, condoms), no sharing needles, medication to reduce transmission (i.e., PrEP).
Yellow Fever
Viral infection transmitted via mosquito bite, found in tropical and subtropical areas in Africa and South America.
Causative Agent(s): Flavivirus (yellow fever virus).
S/S:
- Initial Symptoms: Fever, headache, body aches.
- Severe Symptoms: High fever, yellow skin or eyes (i.e., jaundice), bleeding, shock, organ failure.
Transmission: Mosquito bite.
Dx: Serum testing to detect virus-specific IgM and antibodies.
Tx: Supportive (i.e., rest, fluids, over-the-counter pain relievers).
Prevention: Insect repellant, mosquito control measures. Vaccine for at-risk individuals.
Lyme Disease
Most commonly tickborne infection in the U.S.
Causative Agent(s): Borrelia burgdorferi.
S/S:
- Early Localized: Erythema migrans (i.e., "bullseye" rash), fever, headache, fatigue.
- Early Disseminated: Severe headache, neck stiffness, facial palsy, arthritis.
- Late Disseminated: Severe arthritis, neurological problems.
Transmission: Tick bite. Ticks acquire bacteria from small mammals and birds that act as reservoirs for the bacteria.
Dx: Erythema migrans rash and tick exposure. Serological testing.
Tx: Antibiotics (e.g., doxycycline).
Prevention: Repellents with DEET, protective clothing, remove ticks promptly.
Infective Endocarditis
Bacterial infection of the inner lining of the heart and heart valves.
Causative Agent(s): MANY! Most commonly caused by Staphylococcus aureus and Streptococcus spp.
S/S: Fever, chills, heart murmur, chest pain, night sweats, shortness of breath.
Transmission: Causative agent enters the bloodstream and travels to the heart.
RF: Heart conditions (e.g., prosthetic heart valve, valvular heart disease), IV drug use, poor dental health.
Dx: Blood cultures, echocardiogram.
Tx: Antibiotics, heart valve repair or replacement.
Prevention: Good dental hygiene, antibiotic prophylaxis before dental work or invasive procedures for high-risk individuals.
Toxic Shock Syndrome (TSS)
Serious toxin-mediated disease that can lead to sepsis and organ failure.
Causative Agent(s): Toxin produced by Staphylococcus aureus or Streptococcus pyogenes.
S/S: Fever, rash, low blood pressure, headache, confusion, muscle aches, diarrhea, nausea, vomiting.
Transmission: TSS cannot be spread to others.
RF: Tampon use, skin wounds.
Dx: Clinical signs/symptoms, blood culture, culture from suspected source.
Tx: Remove source of bacteria. IV fluids, antibiotics, immunoglobulin G, and medications to increase blood pressure.
Prevention: Avoid high absorbency tampons, change tampons frequently.
Sepsis
Body's extreme response to a bacterial, viral, or fungal infection.
Causative Agent(s): MANY! Common causative agents include Staphylococcus aureus, Streptococcus pyogenes, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa.
S/S: Fever, high heart rate, shortness of breath, confusion, extreme pain, clammy skin.
Sepsis can lead to septic shock, which causes blood pressure to drop to a dangerous level, which can result in organ failure and death.
Transmission: Causative infection can be spread to others, but sepsis is not spread to other people.
Dx: Physical assessment findings and blood cultures to identify underlying infectious agent.
Tx: Antibiotics, oxygen, IV fluids, medications to ↑ blood pressure.
Aspergillosis
Fungal lung infection that typically affects immunocompromised individuals, causing asthma-like symptoms.
Causative Agent(s): Aspergillus mold, a common mold found indoors and outdoors.
S/S: Wheezing, shortness of breath, cough, congestion, headache.
Transmission: Inhalation of Aspergillus spores. Not spread from person-to-person.
Most people breathe in Aspergillus spores everyday without getting sick.
Dx: Chest x-ray, laboratory analysis of respiratory fluid sample or tissue biopsy.
Tx: IV antifungal agent (e.g., itraconazole).
Coccidioidomycosis
Lung infection caused by a dimorphic fungus. Commonly referred to as "valley fever", as the fungus is endemic in San Joaquin Valley in California.
Causative Agent(s): Coccidioides immitis.
S/S: Fatigue, cough, fever, shortness of breath, headache, night sweats, muscle aches, rash.
Transmission: Inhalation of fungal spores. Not spread from person-to-person.
Dx: Blood test to check for Coccidioides antibodies or antigens, fungal sputum culture.
Tx: Usually self-limiting, antifungal agent for disseminated infections.
Histoplasmosis
Lung infection caused by a fungus that is typically found in the soil, or in bird or bat droppings.
Causative Agent(s): Histoplasma capsulatum.
This fungus is primarily found in areas around the Ohio and Mississippi river valleys.
S/S: Fever, chills, cough, fatigue, headache, chest pain, body aches.
Transmission: Inhalation of fungal spores. Not spread from person-to-person.
Dx: Chest x-ray, antigen detection test using blood or urine sample, fungal sputum culture.
Tx: Usually self-limiting, antifungal agent (e.g., amphotericin B) for severe cases.
Herpes Zoster
Viral illness caused by reactivation of the varicella zoster virus after a chickenpox infection. Commonly referred to as shingles.
Causative Agent(s): Varicella zoster virus (VZV).
S/S: Fever. Pain or tingling where rash will develop, followed by a painful rash on one side of the face or body.
Transmission: Caused by reactivation of varicella zoster virus.
An individual with shingles can infect susceptible individuals with the varicella zoster virus, causing chickenpox.
Dx: Visual examination of rash, examination of vesicular fluid.
Tx: Antiviral agents (e.g., acyclovir), symptom relief (e.g., calamine lotion, pain medication).
Prevention: Shingles vaccine.
Chickenpox
Viral illness caused by the varicella zoster virus. After chickenpox infection, the virus becomes dormant in the nerve cells, but can later become reactivated to cause herpes zoster (i.e., shingles).
Causative Agent(s): Varicella zoster virus (VZV).
S/S: Rash (itchy, fluid-filled blisters that burst and turn into scabs), fever, tiredness, loss of appetite, headache.
Transmission: Breathing in airborne particles, contact with skin lesions.
Chickenpox is contagious until all lesions have crusted over.
Dx: Visual examination of rash, vesicle fluid examination.
Tx: Symptom relief (e.g., calamine lotion, acetaminophen for pain). Antiviral agents (e.g., acyclovir) for individuals at risk for serious complications.
Prevention: Varicella vaccine.
Rubella
Mild viral illness, also known as German measles. TORCH infection.
Causative Agent(s): Rubella virus.
S/S: Low-grade fever, headache, sore throat. Rash that starts on the face and spreads to the rest of the body.
A rubella infection during pregnancy can result in severe birth defects.
Transmission: Respiratory droplets (e.g., coughing, sneezing).
Dx: Blood test to detect rubella-specific antibodies, nasal/throat swab and culture.
Tx: Supportive care for fever and pain.
Prevention: MMR vaccine.
Measles (Rubeola)
Highly contagious viral illness.
Causative Agent(s): Measles virus.
S/S: High fever, cough, runny nose, conjunctivitis. Appearance of Koplik spots (i.e., white spots inside the mouth) 2 - 3 days after symptom onset. Rash appears 3 - 5 days after symptom onset, starting on the face and spreading downward to the rest of the body.
Transmission: Respiratory droplets (e.g., coughing, sneezing), breathing contaminated air, direct contact with contaminated surfaces.
Dx: Blood test to detect measles-specific IgM antibodies, detection of measles RNA in respiratory specimen.
Tx: Supportive care (e.g., fluids, rest, fever control, isolation from others).
Prevention: MMR vaccine.
Respiratory Syncytial Virus (RSV) Infection
Common viral infection that causes mild, cold-like symptoms in most individuals. ↑ Risk of severe infection in infants and older adults.
Causative Agent(s): Respiratory syncytial virus.
S/S: Congestion, coughing, sneezing, fever, decreased appetite, wheezing.
Transmission: Respiratory droplets (e.g., sneezing, coughing).
Dx: Clinical assessment, detection of virus in nasal secretion specimen.
Tx: Supportive care (e.g., fever control, ↑ fluids, oxygen).
Prevention: RSV vaccine for adults ≥ 60 years and during pregnancy to protect infants. RSV antibody immunization for infants and at-risk toddlers.
Influenza
Communicable viral illness that affects the respiratory tract. Commonly referred to as the "flu".
Causative Agent(s): Influenza virus A, B, C, and D.
S/S: Fever, chills, cough, sore throat, congestion, body aches, headache.
Transmission: Respiratory droplets (e.g., sneezing, coughing).
Dx: Rapid influenza diagnostic test (RIDT) or rapid molecular assay using nasal/throat swab.
Tx: Antiviral agents (e.g., zanamivir, oseltamivir), most effective within 1 - 2 days of symptom onset.
Prevention: Annual influenza vaccine.
Card 88
Common Cold
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Answer
Common Cold
Mild viral infection of the nasal cavity.
Causative Agent(s): Rhinoviruses (most common), coronaviruses, adenoviruses.
S/S: Sneezing, cough, runny nose, headache, body aches, sore throat.
Transmission: Respiratory droplets (i.e., coughing, sneezing), contact with contaminated surfaces.
Dx: Clinical assessment; diagnostic testing not necessary.
Tx: Self-limiting. Symptom relief (e.g., decongestants, antihistamines, rest, increased fluid intake).
Legionnaires' Disease
Atypical pneumonia associated with bacterial contamination of human-made water systems (e.g., cooling towers in large buildings).
Causative Agent(s): Legionella pneumophila.
S/S: Cough, shortness of breath, fever, muscle aches, headache.
Transmission: Inhalation of small droplets of water in the air that contain bacteria. Not spread from person-to-person.
Dx: Chest x-ray, sputum culture, urinary antigen test.
Tx: Antibiotics (e.g., levofloxacin, azithromycin).
Tuberculosis (TB)
Bacterial infection that causes inflammation and the formation of granulomas (i.e., clusters of immune cells) in the lungs.
Causative Agent(s): Mycobacterium tuberculosis.
S/S: Cough with blood or sputum, fever, chills, weight loss, night sweats.
Transmission: Airborne (e.g., spread via speaking, coughing).
Dx: Mantoux tuberculin skin test, chest x-ray, sputum culture, blood test.
Tx: Combination of drugs (e.g., rifampin, isoniazid, pyrazinamide, ethambutol).
Prevention: BCG vaccine, used in countries where TB is common.
Card 91
Otitis Media
Causative Agent(s)
Signs/Symptoms
Transmission
Diagnosis
Treatment
Prevention
Answer
Otitis Media
Inflammation and/or infection of the middle ear.
Causative Agent(s): Streptococcus pneumoniae, Haemophilus influenzae.
S/S: Ear pain, fever, irritability, tugging at ear, difficulty sleeping.
Transmission: Secondary infection caused by trapped bacteria in the eustachian tube. Not contagious, but the bacteria or virus causing the infection are.
Dx: Clinical signs/symptoms, otoscopy.
Tx: Antibiotics (e.g., amoxicillin).
Prevention: Hib, influenza, and pneumococcal vaccines.
Streptococcal Pharyngitis (Strep Throat)
Contagious bacterial infection that causes a sore throat. Commonly known as "strep throat".
Causative Agent(s): Streptococcus pyogenes.
S/S: Sore throat, pain with swallowing, fever, red/swollen tonsils, petechiae (tiny, red spots) on roof of mouth, swollen lymph nodes in neck.
Transmission: Respiratory droplets (e.g., coughing, sneezing), direct contact with secretions (e.g., saliva) of an infected person.
Dx: Rapid antigen test or throat culture.
Tx: Antibiotics (e.g., penicillin, cephalexin).
Left untreated, can lead to scarlet fever, rheumatic fever, and glomerulonephritis.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Wolbachia spp. N/A in humans
Gram-negative, pleomorphic, obligate intracellular bacterium. Alters the reproductive system of insects. Provides a valuable tool to manipulate mosquito populations, reducing the transmission of arboviral infections.
Yellow Fever virus
Yellow fever (card 319)
Enveloped, single-stranded RNA virus. Transmitted via the bite of an infected mosquito.
Yersinia pestis
Plague (card 314)
Gram-negative bacterium. Rod-shaped, facultative anaerobe. Found in rodents and their fleas.
Zika virus
Zika (card 334)
Enveloped, single-stranded RNA virus. Transmitted via the bite of an infected mosquito. TORCH infection.
Card 95
Microbes A → Z: Infections & Characteristics
Varicella zoster virus (VZV)
Vibrio cholerae
West Nile virus
Answer
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Varicella zoster virus (VZV)
Chickenpox (card 304), herpes zoster, also known as "shingles" (card 305)
Enveloped, double-stranded DNA virus. After chickenpox infection, VZV stays in the sensory nerve ganglia as a latent infection. Reactivation causes shingles. TORCH infection. Vaccine-preventable.
Vibrio cholerae
Cholera (card 349)
Gram-negative bacterium. Comma-shaped, facultative anaerobe. Highly motile. Infects the small intestine and secretes cholera toxin that alters electrolyte channels.
West Nile virus
Arboviral encephalitis (card 333), meningitis (card 328)
Enveloped, single-stranded RNA virus. Transmitted to humans via the bite of a mosquito. Able to cross blood-brain barrier, causing CNS damage.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Treponema pallidum
Syphilis (card 365)
Gram-negative bacterium. Outer membrane lacks lipopolysaccharide. Spirochete-shaped, anaerobic. Obligate human parasite. TORCH infection.
Trichomonas vaginalis
Trichomoniasis, also known as "trich" (card 369)
Protozoan parasite. Motile. Colonizes the lower genitourinary tract of females and the prostate and urethra of males. Releases cytotoxic proteins that destroy the epithelial lining.
Trypanosoma spp.
American trypanosomiasis, also known as "Chagas disease" (card 326), African trypanosomiasis, also known as "sleeping sickness" (card 338)
Protozoan parasite. T. brucei is transmitted via the bite of a tsetse fly, and T. cruzi is transmitted via the bite of a reduviid insect (i.e., kissing bug).
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Taenia spp.
Taeniasis (card 359), neurocysticercosis or cysticercosis (card 339)
Hermaphroditic tapeworm. Ingestion of larvae from contaminated meat causes taeniasis. Ingestion of T. solium eggs causes cysticercosis or neurocysticercosis. Humans are definitive hosts. Intermediate hosts include cattle for T. saginata (beef tapeworm) and swine for T. solium (pork tapeworm).
Toxoplasma gondii
Toxoplasmosis (card 325)
Obligate intracellular protozoan that infects warm-blooded animals, including humans. TORCH infection.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Streptococcus pyogenes
Streptococcal pharyngitis, also known as "strep throat" (card 292), impetigo (card 372), necrotizing fasciitis (card 373), cellulitis, toxic shock syndrome (card 310), scarlet fever, rheumatic fever, glomerulonephritis
Gram-positive bacterium, coccus-shaped, β-hemolytic, facultative anaerobe. Commonly referred to as group A streptococcus (GAS). Produces a variety of toxins and enzymes that cause tissue damage and destruction of RBCs.
Sulfolobus spp.
N/A
Thermoacidophilic archaea. Grows optimally at 75 - 80 °C and pH 2 - 3. Used in biotechnology for the production of thermostable and acid- resistant proteins.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Streptococcus agalactiae
Group B Streptococcus infections
Gram-positive bacterium. Coccus-shaped, facultative anaerobe. Often colonizes the GI and vaginal tract of women, but can cause a life-threatening neonatal infection if transmitted to the newborn during vaginal birth.
Streptococcus mutans
Dental caries (card 341)
Gram-positive bacterium. Coccus-shaped, facultative anaerobe. Lives in the mouth, able to form dense biofilms. Leading cause of tooth decay.
Streptococcus pneumoniae
Otitis media (card 294), pneumonia (card 291), meningitis (card 328)
Gram-positive bacterium. Lancet-shaped coccus, facultative anaerobe. Some strains produce capsules. Commonly found in the nasopharynx of healthy individuals. Many strains are drug resistant. Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Shigella spp.
Shigellosis, also known as "bacillary dysentery" (card 345)
Gram-negative bacterium. Rod-shaped, facultative anaerobe. Tolerant of low pH, able to survive in the stomach. S. dysenteriae type 1 produces Shiga toxin, causing severe disease.
Smallpox virus
Smallpox (card 382)
Enveloped, double-stranded DNA virus. Infection previously caused significant morbidity and mortality, but smallpox was eradicated with vaccination.
Staphylococcus aureus
MANY, including skin infections (cards 371, 372, 373, 375), endocarditis (card 311), staphylococcal food poisoning (card 344), toxic shock syndrome (card 310)
Gram-positive bacterium. Coccus-shaped, facultative anaerobe, β-hemolytic. Part of the normal flora on the skin and mucous membranes. Can cause serious infections if allowed to enter internal tissues or the bloodstream. Some strains produce toxins, some strains are drug resistant (e.g., methicillin-resistant S. aureus, MRSA).
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Schistosoma spp. Schistosomiasis, also known as "bilharzia" (card 327)
Parasitic worm. After penetration of the skin, parasites mature and live in the blood vessels. Eggs released by females pass in the urine/ feces or travel to the intestine or bladder, causing inflammation and organ damage.
Freshwater snails are the intermediate host and humans are the definitive host for the parasite.
Serratia marcescens
MANY, including urinary tract infection (card 360), pneumonia (card 291), wound infections
Gram-negative bacterium. Rod-shaped, facultative anaerobe. Produces a red pigment at room temperature. Opportunistic pathogen, frequently associated with hospital-acquired infections.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Saccharomyces cerevisiae
N/A unless immunocompromised
Unicellular fungus (yeast), referred to as "baker's yeast". Instrumental in the production of bread products and alcoholic beverages.
Salmonella spp.
Salmonellosis (card 346), typhoid fever (card 347)
Gram-negative bacterium. Rod-shaped, facultative anaerobe. Invades the intestinal epithelium. Typhoid toxin produced by S. typhi causes typhoid fever.
SARS-Coronavirus-2
COVID-19 (card 301)
Enveloped, single-stranded RNA virus. Appearance resembles a crown due to club-shaped surface proteins (corona in Latin = crown). Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Rickettsia rickettsii
Rocky Mountain spotted fever (card 315)
Gram-negative bacterium. Pleomorphic, aerobic. Obligate intracellular parasite. Infects endothelial cells in the blood vessels.
Rotavirus
Viral gastroenteritis (card 354)
Non-enveloped, double-stranded RNA virus. Replicates in the epithelium of the small intestine, spreads primarily through the fecal- oral route. Very stable in the environment.
Rubella virus
Rubella, also known as "German measles" (card 303)
Enveloped, single-stranded RNA virus. After respiratory transmission, replicates in the nose, throat, and local lymph nodes. TORCH infection. Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Pseudomonas aeruginosa
MANY, including otitis externa (card 375), urinary tract infection (card 360), pneumonia (card 291), meningitis (card 328), keratitis
Gram-negative bacterium. Rod-shaped, aerobic. Commonly found in freshwater (e.g., pools, hot tubs). Produces a blue-green pigment. Common cause of nosocomial infections. Drug resistant.
Smells like corn tortillas or grape soda!
Common cause of respiratory infections in cystic fibrosis patients or those on mechanical ventilators.
Rabies virus
Rabies (card 335)
Enveloped, single-stranded RNA virus. Infects neurons in the central nervous system.
Card 106
Microbes A → Z: Infections & Characteristics
Prions
Proteus mirabilis
Answer
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Prions
Transmissible Spongiform Encephalopathies
(card 337)
Acellular pathogenic agents that cause normal protein found in the brain (PrPC) to misfold into a disease-causing form (PrPSc). Spread through contact with infected tissues or ingestion of contaminated meat. Disease also caused by spontaneous transformation of normal proteins, or inherited mutations of the prion protein gene.
Proteus mirabilis
Urinary tract infection (card 360)
Gram-negative bacterium. Rod-shaped, facultative anaerobe. Demonstrates swarming motility. Produces urease, which ↑ the pH in the urinary tract, leading to formation of stones.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Penicillium spp.
Penicilliosis
Common fungus, decomposes organic material. Used to make penicillin, which revolutionized medical care. Infection typically only occurs in immunocompromised hosts.
Plasmodium spp.
Malaria (card 324)
Protozoan parasite transmitted via an infected mosquito. After a mosquito bite, sporozoites travel through the bloodstream to the liver, where they mature and release merozoites. Merozoites then infect and multiply within RBCs.
Humans are the intermediate hosts and mosquitoes are the definitive hosts for the parasite.
Poliovirus
Poliomyelitis (card 336)
Non-enveloped, single-stranded RNA virus. Spreads by fecal-oral route, aerosols, or droplets. Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Neisseria gonorrhoeae
Gonorrhea (card 363)
Gram-negative bacterium. Bean-shaped diplococcus, obligate aerobe. Drug resistant.
Neisseria meningitidis
Meningitis (card 328)
Gram-negative bacterium. Bean-shaped diplococcus, aerobic. Spread by respiratory secretions and saliva. 10% of the general population carries the bacteria in their nose and throat without adverse effects. Vaccine-preventable.
Norovirus
Viral gastroenteritis (card 354)
Non-enveloped, single-stranded RNA virus. Resistant to common disinfectants, extremely stable in the environment.
Parvovirus B19
Fifth disease, also known as "erythema infectiosum" (card 380)
Non-enveloped, single-stranded DNA virus. Only parvovirus that is pathogenic to humans (vs. animals). TORCH infection.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Mycobacterium tuberculosis
Tuberculosis (card 295)
Gram-positive bacterium. Acid-fast, rod-shaped, obligate aerobe. Survives phagocytosis due to mycolic acid in the cell wall. Drug resistant.
Mycoplasma pneumoniae
Pneumonia (card 291)
Bacterium lacks a cell wall, able to alter size/shape, facultative anaerobe. Attaches to and damages the respiratory epithelial cells. Produces a toxin that causes inflammation and airway dysfunction. Common cause of "walking pneumonia".
Naegleria fowleri
Primary amoebic meningoencephalitis (card 340)
Protozoan that lives in soil and warm fresh water (e.g., lakes, hot springs). Commonly called "brain-eating amoeba" due to its ability to cause a fatal brain infection.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Methanobacterium spp.
N/A
Anaerobic archaea that produce methane gas. They live in extreme environments and are able to reproduce at temperatures from below freezing to boiling.
Mumps virus
Mumps (card 343)
Enveloped, single-stranded RNA virus. Spread by respiratory droplets and saliva. Vaccine- preventable.
Mycobacterium leprae
Hansen's disease, also known as "leprosy" (card 332)
Gram-positive bacterium. Acid-fast, rod-shaped, microaerophilic. Binds to and invades Schwann cells in the nervous system. Affects extremities due to a lower optimum growth temperature. Drug resistant. 95% of the world's population possess a natural immunity to this bacterium.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Leptospira spp.
Leptospirosis, also known as "Weil's disease" (card 361)
Gram-negative bacterium. Spirochete-shaped, obligate aerobe. Spread through the urine of infected animals.
Listeria monocytogenes
Listeriosis (card 331)
Gram-positive bacterium. Rod-shaped, facultative anaerobe. Can grow at refrigerator temperatures. Crosses the blood-brain and placenta-fetus barrier. TORCH infection.
Measles virus
Measles, also known as "rubeola" (card 302)
Enveloped, single-stranded RNA virus. Spread through coughing or sneezing, breathing contaminated air, or touching contaminated surfaces. One of the most contagious infectious agents. Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Klebsiella pneumoniae
Pneumonia (card 291), sepsis (card 309), urinary tract infection (card 360)
Gram-negative bacterium. Rod-shaped, encapsulated, facultative anaerobe. Frequent cause of nocosomial infections (i.e., healthcare-associated infections).
Lactobacillus acidophilus
N/A unless immunocompromised
Gram-positive bacterium. Rod-shaped, microaerophilic. Important intestinal and vaginal probiotic, providing many health benefits. Used in the production of fermented foods such as yogurt.
Legionella pneumophila
Legionnaires' disease (card 297)
Gram-negative bacterium. Rod-shaped, motile, aerobic. Grows in human-made water systems (e.g., cooling towers) and is transmitted to susceptible hosts via aerosolization.
Legionella pneumophila is not contagious.
Card 113
Microbes A → Z: Infections & Characteristics
Human immunodeficiency virus (HIV)
Human papillomavirus (HPV)
Influenza virus
Answer
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Human immunodeficiency virus (HIV)
HIV (card 323)
Enveloped RNA retrovirus. Destroys CD4+ cells in the immune system. High mutation rate allows for evasion of the host immune system. TORCH infection.
Human papillomavirus (HPV)
HPV infection (card 367), papillomas, also known as "warts" (card 377)
Non-enveloped, double-stranded DNA virus. Certain strains can inactivate tumor suppressor proteins in the host, leading to uncontrolled cell division and the development of cancer. Certain strains are vaccine-preventable.
Influenza virus
Influenza (card 299)
Enveloped, single-stranded RNA virus. Vaccine-preventable. Rapid mutations of surface proteins allows for evasion of the host immune system and requires annual modifications to the influenza vaccine.
Although it is an RNA virus, influenza replicates in the nucleus.
Card 114
Microbes A → Z: Infections & Characteristics
Herpes simplex virus (HSV)
Histoplasma capsulatum
Human herpesvirus type 6
Answer
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Herpes simplex virus (HSV)
Oral herpes, also known as "cold sores" or "fever blisters" (card 378), genital herpes (card 366)
Enveloped, double-stranded DNA virus. HSV-1 most commonly causes oral herpes, HSV-2 most commonly causes genital herpes. After infection, virus becomes dormant in the nervous system and can later become reactivated. TORCH infection.
Histoplasma capsulatum
Histoplasmosis (card 306)
Fungus found in the environment, especially in soil that contains bird or bat droppings. Disease caused from inhalation of fungal spores.
Human herpesvirus type 6
Roseola, also known as "roseola infantum" or "sixth disease" (card 379)
Encapsulated, double-stranded DNA virus. Primarily infects infants and causes more serious illness in immunocompromised individuals.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Helicobacter pylori
Peptic ulcer disease (card 351)
Gram-negative bacterium. Spiral-shaped, motile, microaerophilic. Urease (i.e., an enzyme) allows bacteria to survive in the stomach's low pH environment. Toxins cause stomach mucosal inflammation and tissue damage.
Hepatitis viruses
Viral hepatitis (card 355)
A group of viruses that cause liver inflammation and damage. Hepatitis B is a TORCH infection. Hepatitis A and B are vaccine-preventable.
Hepatitis A: Nonenveloped single-stranded RNA virus.
Hepatitis B: Enveloped double-stranded DNA virus.
Hepatitis C: Enveloped single-stranded RNA virus.
Hepatitis D: Enveloped single-stranded RNA virus.
Hepatitis E: Quasi-enveloped single-stranded RNA virus.
Each hepatitis virus comes from a different viral family.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Giardia lamblia (Giardia duodenalis)
Giardiasis (card 356)
Flagellated, anaerobic, protozoan parasite. Lacks mitochondria. Replicates in the small intestine and is transmitted to the next host via the fecal-oral route.
Causative agent of beaver fever!
Haemophilus influenzae
Pneumonia (card 291), meningitis (card 328), otitis media (card 294), epiglottitis, cellulitis
Gram-negative bacterium. Coccobacillus-shaped, facultative anaerobe. Despite its name, it does not cause flu (i.e., influenza). H. influenzae type b (i.e., Hib) is the most common subtype. Vaccine-preventable.
Halobacterium spp.
N/A
Halophilic archaea. Rod-shaped, motile, pink-pigmented. Requires an environment with high concentration of salt (i.e., Dead Sea).
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Escherichia coli
Diarrheagenic E. coli infection (card 348), urinary tract infection (card 360), pneumonia (card 291)
Gram-negative bacterium. Rod-shaped bacillus, facultative anaerobe. Part of the normal intestinal microbiota, but can cause a variety of infections when found outside the intestinal tract. Specific strains produce toxins that cause watery or bloody diarrhea, or hemolytic uremic syndrome.
Gardnerella vaginalis
Bacterial vaginosis (card 362)
Gram-positive cell wall, but regarded as a Gram-variable organism. Bacillus-shaped, anaerobic. Part of the normal vaginal microbiota, overgrowth leads to BV.
Get a clue! Microscopic assessment of BV by Gram stain shows clue cells, which are vaginal epithelial cells covered with Gram-variable bacilli.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Ebolaviruses
Ebola disease (card 322)
Enveloped, single-stranded RNA viruses. Primarily found in sub-Saharan Africa. Causes severe hemorrhagic fever, high mortality rate.
Enterobius vermicularis
Enterobiasis, also known as "pinworm" (card 358)
Small, thin, white roundworm. Primarily lives in the intestines of humans, infection spread through fecal-oral route. Most common helminth infection in U.S.
Epstein Barr virus (EBV)
Infectious mononucleosis, also known as "mono" (card 317)
Enveloped, double-stranded DNA virus. Also known as human herpesvirus 4. EBV linked to the development of several types of cancer.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Deinococcus radiodurans
N/A
Gram-positive bacterium. Elliptical-shaped, aerobic. Extremely resistant to ionizing radiation.
Literal translation of this organism's name is "strange berry that withstands radiation".
Dengue virus
Dengue fever (card 320)
Enveloped, single-stranded RNA virus. Mosquito-transmitted virus. More common in tropical/sub-tropical climates and in urban areas.
Dracunculus medinensis
Dracunculiasis, also known as "Guinea worm disease"
Parasitic worm, spread by drinking unfiltered water containing microscopic infected copepods or by consuming raw, infected aquatic animals. Affects poor communities in remote parts of Africa.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Cryptosporidium spp.
Cryptosporidiosis, also known as "crypto" (card 357)
Protozoan parasite. Lives in the intestines of infected humans or animals. Shed in the stool, transmitted via fecal-oral route.
Cutibacterium acnes
Acne (card 370)
Gram-positive bacterium. Rod-shaped, facultative anaerobe. Normal part of the skin microbiota. Secretion of fatty acids contributes to the acidic pH of the skin.
Formerly known as Propionibacterium acnes.
Cytomegalovirus
Cytomegalovirus disease (card 318)
Enveloped, double-stranded DNA virus. Member of the herpesviruses. After infection, virus remains latent and can become reactivated at a later time. TORCH infection.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Coccidioides immitis
Coccidioidomycosis, also known as "valley fever" (card 307)
Dimorphic fungus found in arid deserts with high salt content (e.g., San Joaquin Valley in California). Disease occurs from inhalation of fungal spores.
Corynebacterium diphtheriae
Diphtheria (card 293)
Gram-positive bacterium. Club-shaped rods, anaerobic. Diphtheria toxin blocks protein synthesis, leading to host cell death. Vaccine-preventable.
Cryptococcus neoformans
Meningitis (card 328)
Fungus found in soil, decaying wood, bird droppings. Inhalation of fungal spores primarily causes disease in immunocompromised individuals.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Clostridium botulinum
Botulism (card 330)
Gram-positive bacterium. Rod-shaped, endospore- forming, obligate anaerobe. Produces botulinum neurotoxins, which cause flaccid paralysis.
The botulinum toxin is one of the most lethal substance known to humans.
Clostridium perfringens
Clostridium perfringens gastroenteritis (card 352), gas gangrene
Gram-positive bacterium. Rod-shaped, endospore- forming, obligate anaerobe. Spores can survive normal cooking temperatures. Produces toxins and enzymes that can lead to destruction of host tissue.
Clostridium tetani
Tetanus (card 329)
Gram-positive bacterium. Drumstick-shaped rod, endospore-forming, obligate anaerobe. Produces exotoxins that block inhibitor impulses in CNS, causing unopposed muscle contractions, resulting in spastic paralysis. Vaccine-preventable.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Chlamydia trachomatis
Chlamydia (card 364)
Gram-negative bacterium. Coccobacillus- shaped, anaerobic. Obligate intracellular pathogen. Metabolically inactive elementary bodies (EBs) infect host cells where they become active reticulate bodies (RBs). The RBs then multiply and form new EBs, which can infect additional cells.
Clostridioides difficile
Clostridioides difficile infection (card 353)
Gram-positive bacterium. Rod-shaped, endospore-forming, obligate anaerobe. Produces exotoxins (toxin A and B). Shed in feces. Items contaminated with feces can become a reservoir for C. diff spores.
Formerly known as Clostridium difficile.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Brucella spp.
Brucellosis, also known as "remitting fever", "undulant fever", or "Mediterranean fever" (card 312)
Gram-negative bacterium. Coccobacillus- shaped, aerobic. Found in the reproductive organs of host animals (e.g., pigs, cattle) and shed in fluids (e.g., urine, milk).
Campylobacter jejuni
Campylobacteriosis (card 350)
Gram-negative bacterium. Curved or S-shaped rod (seagull-wing shaped), motile, microaerophilic. Most common bacterial cause of gastroenteritis. Produces a toxin that damages host DNA.
Candida albicans
Vaginal candidiasis, also known as a "yeast infection" (card 368), thrush, candidiasis of the skin
Unicellular fungus (yeast). Normal part of microbiome, but can cause infections in mmunocompromised individuals or following antibiotic use.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Bartonella henselae
Cat scratch disease (card 313)
Gram-negative bacterium. Rod-shaped, fastidious, aerobic. Cats become infected through flea bites and are usually asymptomatic carriers of the bacteria.
Bordetella pertussis
Pertussis, also known as "whooping cough" (card 296)
Gram-negative bacterium. Coccobacillus- shaped, aerobic. Binds to cilia in the upper respiratory tract. Toxins paralyze the cilia, causing inflammation and the accumulation of mucus. Vaccine-preventable.
Borrelia burgdorferi
Lyme disease (card 316)
Gram-negative bacterium. Spirochete-shaped, motile, microaerophilic. Spreads to people through the bite of an infected tick. Most common vector-borne disease in the U.S.
Microbes A → Z: Infections & Characteristics
Microbe & Infection(s)
Characteristics
Ascaris lumbricoides
Ascariasis
Parasitic worm that lives in the intestine. Ascaris eggs are passed in the feces of infected individuals, disease is caused from ingestion of worm eggs. Found in areas with poor hygiene and sanitation practices.
Aspergillus spp.
Aspergillosis (card 308)
Filamentous fungus. Found in soil, decaying vegetation, seeds, and grains. Opportunistic pathogen that affects immunocompromised hosts.
Bacillus anthracis
Anthrax (card 374)
Gram-positive bacterium. Rod-shaped, endospore-forming, facultative anaerobe. Commonly found in soil. Exotoxins cause edema and tissue damage.
Potential agent of bioterrorism.
Card 127
Epidemiology
Centers for Disease Control & Prevention (CDC)
Notifiable Diseases
World Health Organization (WHO)
Emerging Infectious Diseases
Reemerging Infectious Diseases
Answer
Epidemiology
Centers for Disease Control & Prevention (CDC): National public health agency for the United States.
Notifiable Diseases: Diseases considered to be of great public health importance. Cases must be reported to the state and/or CDC for monitoring on a national scale (e.g., HIV, measles).
World Health Organization (WHO): Agency of the United Nations responsible for international public health issues.
Emerging Infectious Diseases: Diseases that are new to the human population, or existing diseases that are rapidly spreading (e.g., COVID-19).
Reemerging Infectious Diseases: Diseases that are increasing in frequency after a period of decline (e.g., measles).
Epidemiology
Descriptive Epidemiology: Gathers information about a disease outbreak by interviewing patients and their contacts and analyzing medical test results.
Retrospective Epidemiology: Uses historical data to identify associations with present-day cases of a disease.
Prospective Epidemiology: Gathers data and follows individuals to find and identify factors that contribute to future disease states.
Analytical Epidemiology: Observes groups of individuals to uncover associations between environmental or genetic factors and disease.
Experimental Epidemiology: Use of test subjects and control subjects to study connections between diseases and causative agents, or to evaluate treatments.
Disease Occurrence
Endemic: Constant presence of a disease in a geographic area (e.g., Lyme disease in Northeast U.S., malaria in sub-Saharan Africa).
Epidemic: A sudden increase in the number of cases of a disease above what is expected in a population (e.g., influenza).
Pandemic: Epidemic has spread to several countries and/or continents, affecting a large number of people (e.g., HIV/AIDS, COVID-19).
Sporadic: Disease occurs irregularly and infrequently (e.g., tetanus, plague).
Epidemiology
Study of how a disease originates and spreads through a population, with a goal of detecting and controlling outbreaks.
Etiology: The cause of a disease or condition.
Morbidity: State of having a disease or condition. Measures of morbidity include prevalence and incidence.
Prevalence: The number or proportion of people with a particular illness in a given population at a certain point in time.
Incidence: The number or proportion of new cases of a particular illness in a given period of time.
Mortality: Death. Mortality rate is expressed as the # of deaths from a disease per standard # of people (e.g., 100,000 people).
Common Source Spread: There is a single source for all infected individuals.
Propagated Spread: Infection is spread through person-to-person contact.
Diagnostic Immunology
Agglutination Test
Enzyme-Linked Immunosorbent Assay (ELISA)
Fluorescent Antibody Test
Answer
Diagnostic Immunology
Agglutination Test: Sample with the unknown antigen/antibody is mixed with known antibodies/antigens to see if agglutination (i.e., clumping of cells) occurs.
ELISA: Presence of a unique antibody or antigen of interest is identified in a patient sample using modified antibodies fused to an enzyme that reacts with a substrate to alter color of the sample.
Fluorescent Antibody Test: Fluorescent marker is attached to an antibody. Binding of the antibody to an antigen in the patient sample causes illumination that is easily visible with a fluorescence microscope.
Card 133
Monoclonal Antibodies
Illustration
Answer
Monoclonal Antibodies
Card 134
Polyclonal Antibodies
Illustration
Answer
Polyclonal Antibodies
Card 135
Immune System Disorders: Immunodeficiency
Primary Immunodeficiency
Secondary Immunodeficiency
Answer
Immune System Disorders: Immunodeficiency
Elements of the immune system are absent or defective, causing increased susceptibility to infection.
Primary Immunodeficiency: Inherited defects in the innate or adaptive immune defenses (e.g., severe combined immunodeficiency, X-linked agammaglobulinemia).
Secondary Immunodeficiency: Acquired defects that impair immune function. Caused by systemic disorders (e.g., AIDS, diabetes), immunosuppressive therapy (e.g., chemotherapy, radiation), or a prolonged critical illness. Often reversible if the underlying cause is addressed.
Card 136
Immune System Disorders
Hypersensitivity
Autoimmune Disorder
Answer
Immune System Disorders
Hypersensitivity: Exaggerated or inappropriate response upon exposure to an antigen, resulting in inflammation and destruction of healthy tissue (e.g., allergies, blood transfusion reactions, serum sickness, tissue transplant rejection).
Autoimmune Disorder: Body's normal defenses recognize self-antigens as foreign and target them. Caused by genetic, hormonal, and environmental factors (e.g., Type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis, celiac disease, multiple sclerosis).
Vaccines
Substances that expose an individual to pathogen-specific antigens. Used to stimulate adaptive immunity.
Live Attenuated Vaccine: Contains a live, weakened pathogen (e.g., MMR vaccine).
Inactivated Vaccine: Contains an inactivated or killed pathogen (e.g., hepatitis A vaccine).
Subunit Vaccine: Contains an antigen of a pathogen, not the whole cell or virus (e.g., hepatitis B vaccine).
Toxoid Vaccine: Contains inactivated bacterial toxins (e.g., tetanus vaccine).
Conjugate Vaccine: Contains polysaccharides combined with proteins (e.g., Hib conjugate vaccine). Yields a better response in young children.
Nucleic Acid Vaccine: Contains genetic material (DNA or RNA) from the pathogen, prompting the body to produce proteins that stimulate an immune response (e.g., COVID-19 vaccine).
Card 138
Types of Adaptive Immunity
Active Natural Immunity
Active Artificial Immunity
Passive Natural Immunity
Passive Artificial Immunity
Answer
Types of Adaptive Immunity
Active Natural Immunity: Body produces antibodies in response to exposure to a live pathogen.
Active Artificial Immunity: Body produces antibodies in response to exposure to a vaccine.
Passive Natural Immunity: Mother passes antibodies to her baby through the breast milk or the placenta.
Passive Artificial Immunity: Antibodies are administered to an individual.
With active immunity, the body is exposed to an antigen, triggering an immune response. With passive immunity, the body is given antibodies, but it does not trigger an immune response.
Adaptive Immunity
Primary Response: First exposure to a pathogen triggers activation of B and T cells. IgM is the first antibody made during the primary response.
Secondary Response: Subsequent exposure to the same pathogen is faster and stronger as a result of memory cells produced during the primary response. IgG is the primary antibody involved in the secondary response.
Card 140
Adaptive Immunity: Cellular Immunity
Illustration:
- Cytotoxic T Cell Activation
Adaptive Immunity: Cellular Immunity
Helper T Cells
Regulatory T Cell
Cytotoxic T Cells
Answer
Adaptive Immunity: Cellular Immunity
Helper T Cells: CD4+ cells. Activated by APCs presenting antigens with MHC II. Coordinate humoral and cellular immunity. Involved in activation of macrophages and natural killer cells.
Regulatory T Cells: CD4+ cells. Activated by APCs presenting antigens with MHC II. Prevent hypersensitivity (i.e., overreaction) of the immune system.
Cytotoxic T Cells: CD8+ cells. Activated by cells presenting antigens with MHC I. Recognize and destroy cells infected by intracellular pathogens. Release perforins to create temporary pores in the target cell membrane, allowing granzymes to enter the cell and initiate apoptosis (i.e., cell suicide).
Major Histocompatibility Complexes
Major Histocompatibility Complex I (MHC I)
Major Histocompatibility Complex II (MHC II)
Answer
Major Histocompatibility Complexes
MHC I: Molecules presented on all nucleated cells. Cells present a fragment of a "normal self" antigen on MHC I. If they become infected, they present a fragment of the foreign or "nonself" antigen on MHC I, marking the cell for destruction.
MHC II: Molecules presented only on the surface of antigen-presenting cells (APCs), which include macrophages, dendritic cells, and B cells. APCs present a fragment of a "nonself" antigen on MHC II, which results in Helper T cell activation.
Antigen-Antibody Interactions
Neutralization: Antibody binds to epitopes on the surface of the pathogen or toxin, preventing attachment to the host cell.
Opsonization: Coating of a pathogen by antibodies, which facilitates phagocytosis.
Agglutination: Cross-linking of pathogens by antibodies, causing antigens to clump together. Makes it easier for phagocytes to ingest.
Complement Activation: Classical pathway triggered by binding of IgG or IgM to a pathogen.
Antibody-Dependent Cell-Mediated Cytotoxicity: Facilitates killing of pathogens that are too large to be consumed via phagocytosis.
Card 146
Adaptive Immunity: Antibody Classes
IgG
IgM
IgA
IgD
IgE
Answer
Adaptive Immunity: Antibody Classes
IgG: Accounts for ~80% of antibodies in the blood, produced mostly in the secondary immune response. Crosses the placental barrier in pregnancy.
IgM: Accounts for ~6% of antibodies in the blood. First antibody produced in the primary immune response, making it a valuable diagnosic marker.
IgG and IgM activate complement via the classical pathway.
IgA: Accounts for ~13% of antibodies in the blood. Most common antibody found in secretions (e.g., mucus, saliva, tears, breastmilk).
IgD: Accounts for
IgE: Accounts for
MADGE to remember the 5 antibody classes: IgM, IgA, IgD, IgG, IgE.
Adaptive Immunity
Humoral Immunity: Antibody production by B cells, which provides defense against pathogens in the extracellular environment. B cells mature in the bone marrow and are responsible for the production of antibodies.
Cellular Immunity: Targeting and destruction of intracellular pathogens by T cells. T cells are produced in the bone marrow and travel to the thymus for maturation through the process of thymic selection (i.e., a process where defective T cells are "weeded out"). T cells that do not recognize MHC on host cells or attack host cells are eliminated via apoptosis.
Card 149
Innate Immunity: Phagocytosis
Illustration
Answer
Innate Immunity: Phagocytosis
Card 150
Innate Immunity: Complement System
Opsonization
Inflammation
Membrane Attack Complex (MAC)
Answer
Innate Immunity: Complement System
Opsonization: Coating of a pathogen by a chemical substance (e.g., complement protein C3b) that allows phagocytic cells to recognize, engulf, and destroy it more easily.
Inflammation: Activation of mast cells by complement proteins C3a and C5a causes release of inflammatory chemicals (e.g., histamine). Results in vasodilation, ↑ vascular permeability, and attraction of leukocytes (i.e., white blood cells).
Membrane Attack Complex (MAC): Complement protein C5b recruits C6, C7, C8, and several C9 proteins to form a pore in the membrane of a Gram-negative bacteria, leading to cell lysis and death of the pathogen.
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Innate Immunity: Chemical Defenses
Antimicrobial Peptides
Acute Phase Proteins
Cytokines
Answer
Innate Immunity: Chemical Defenses
Antimicrobial Peptides: Host defense peptides that cause cell damage in pathogens by damaging the plasma membrane, destroying DNA or RNA, or interfering with cell wall synthesis.
Acute Phase Proteins: Proteins secreted into the blood during inflammation. Includes lactoferrin and transferrin, which are iron-binding proteins that deprive pathogens of iron, inhibiting bacterial growth.
Cytokines: Soluble proteins that serve as chemical signals between cells and stimulate a wide range of non-specific defenses. Includes interleukins, chemokines, and interferons.
Interferons "interfere" with viruses (i.e., inhibit viral replication).
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Innate Immunity: Chemical Defenses
Sebum
Sweat
Lysozyme
Saliva
Gastric Juice
Answer
Innate Immunity: Chemical Defenses
Sebum: Produced by sebaceous glands in the skin. Provides an oil barrier, protecting hair follicle pores. Acidity inhibits bacterial growth.
Sweat: Provides a salty and acidic environment on the skin that inhibits the growth of some microbes.
Lysozyme: Enzyme found in secretions (e.g. sweat, mucus, tears, saliva, urine) that destroys bacterial cell walls. More effective with gram-positive bacteria, which lack a protective outer membrane.
Saliva: In addition to lysozyme, contains IgA antibodies that prevent bacterial attachment.
Gastric Juice: Stomach acid, which has a very low pH, kills most pathogens that enter the gastrointestinal tract.
The acidity of urine, cerumen, and vaginal secretions also inhibits bacterial growth.
Immunity
Innate Immunity: Defense mechanisms in the body that respond immediately and non-specifically to antigens. Present at birth, lasts for life. Includes physical defenses, normal microbiota, chemical defenses, cellular defenses, phagocytosis, inflammation, and fever.
Adaptive (Acquired) Immunity: Immune response characterized by specificity (i.e., targeting of specific antigens) and memory (i.e., the ability to respond quickly to pathogens upon reexposure). Includes humoral immunity and cellular immunity.
Virulence Factors
Adherence Factors: Substances (e.g., biofilm, capsule, M protein) or structures (e.g., pili, fimbriae) on the surface of a microorganism that allow it to adhere to host cells.
Capsule: Protects the microorganism from opsonization and phagocytosis.
Antigenic Variation: Alteration of the pathogen's surface antigens so the host's immune system does not recognize it as a pathogen.
Invasion Factors: Mechanisms that enable a microorganism to invade and enter host cells (e.g., invasins).
Exoenzymes: Extracellular enzymes that enable a microbe to invade deeper tissues (e.g., collagenase, protease, coagulase).
Toxins: Biological poisons produced by certain pathogens that damage host cells (e.g., endotoxins, exotoxins).
Siderophores: Substances produced by many bacteria that capture iron from the host.
Virulence & Virulence Factors
Virulence: Pathogenicity (i.e., disease-producing power) of a microorganism. Highly virulent organisms are more likely to cause disease.
Infectious Dose (ID50): A relative number that corresponds to the virulence of a pathogen. It is equal to the number of pathogens required to cause an active infection in 50% of a sample population.
Virulence Factors: Traits that increase a microorganism's ability to invade the host, cause disease, and evade host defenses. Includes unique cellular attributes and specialized proteins.
Symbiosis
Relationship between organisms of different species.
Mutualism: Both organisms benefit.
Neutralism: Both organisms are unaffected.
Commensalism: One organism benefits, the second is unaffected.
Parasitism: One organism benefits, the second is harmed.
Amensalism: One organism is harmed, the second is unaffected.
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Spread of Infectious Diseases
Basic Reproduction Number
Herd Immunity
Answer
Spread of Infectious Diseases
Basic Reproduction Number (R0): Number of susceptible individuals that one infected person can infect.
- R0
- R0 = 1: Each existing infection causes one new infection. Disease will continue, outbreak or epidemic unlikely.
- R0 > 1: Each existing infection causes more than one new infection. Disease is transmitted between individuals, outbreak or epidemic may occur.
Herd Immunity: Occurs when a sufficient percentage of the population is immune to an infectious disease, preventing spread and providing protection to susceptible individuals.
As the R0 value increases, the threshold for reaching herd immunity also increases.
Antibodies
Polyclonal Antibodies: Antibodies produced in a lab setting that recognize multiple epitopes on an antigen and are produced by multiple clones of plasma B cells.
- Rapid and inexpensive production.
- Used in some laboratory screening assays, but shows less specificity than monoclonal antibodies.
Monoclonal Antibodies: Antibodies produced in a lab setting that recognize one specific epitope on an antigen.
- Production is expensive and time-consuming.
- Used in diagnostic laboratory testing and the treatment of certain diseases (e.g., cancers).
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Adaptive Immunity: Cellular Immunity
Cytotoxic T Cell Activation
Cytotoxic T Cell Proliferation
Answer
Adaptive Immunity: Cellular Immunity
Cytotoxic T Cell Activation:
- T Cell Receptor (TCR) on the Cytotoxic T Cell interacts with MHC I on the antigen presenting cell (APC).
- CD8 on Cytotoxic T Cell also interacts with MHC I.
- The T cell and APC cell secrete cytokines that activate the Cytotoxic T Cell.
Cytotoxic T Cell Proliferation: After activation, the Cytotoxic T cell undergoes proliferation and then differentiation into:
- Effector Cytotoxic T Cells: Assist in the immediate immune response. Target intracellular pathogens for destruction. Short-lived.
- Memory Cytotoxic T Cells: Long-lived, programmed to remember a specific antigen to mount a rapid, stronger response upon subsequent exposure.
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Adaptive Immunity: Cellular Immunity
Helper T Cell Activation
Helper T Cell Proliferation
Answer
Adaptive Immunity: Cellular Immunity
Helper T Cell Activation:
- T Cell Receptor (TCR) on the Helper T Cell interacts with the MHC II-Antigen complex on the Antigen Presenting Cell (APC).
- CD4 receptor on the Helper T cell also interacts with MHC II.
Helper T Cell Proliferation: After activation, the Helper T cell undergoes proliferation and then differentiation into:
- Effector Helper T Cells: Includes T helper 1 (TH1) cells and T helper 2 (TH2) cells, which assist in the immediate immune response. Secrete cytokines that enhance immune activity. Short-lived (7 - 30 days).
- Memory Helper T Cells: Long-lived, programmed to remember the specific antigen in order to mount a rapid, stronger response upon subsequent exposure.
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Adaptive Immunity: Humoral Immunity
B Cell Activation
B Cell Proliferation
Answer
Adaptive Immunity: Humoral Immunity
B Cell Activation:
- Antigen binds to a B cell receptor on a B cell. Antigen is internalized and presented on the surface of the B cell with MHC II proteins.
- Helper T cell binds to the complex and releases cytokines, which activate the B cell.
B Cell Proliferation: After activation, B cell undergoes clonal proliferation and then differentiation into:
- Plasma (Effector B) Cells: Produce and release antibodies against that specific antigen. Short-lived (~ 5 days).
- Memory B Cells: Long-lived, programmed to remember the specific antigen in order to mount a rapid, stronger response upon subsequent exposure.
A B cell can also be activated by a T-independent antigen, but the response is weaker and memory B cells are NOT produced.
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Adaptive Immunity
Antigen
Antibody
Answer
Adaptive Immunity
Antigen: Molecular structure on a pathogen that triggers activation of adaptive immunity. Epitopes are smaller, exposed regions on the surface of an antigen. Antibodies and T cells interact with epitopes (vs. the entire antigen).
A hapten is a small molecule that must attach to a larger carrier molecule (e.g., protein) to elicit an immune response.
Antibody: Y-shaped glycoprotein produced by the immune system in response to an antigen. Composed of two heavy chains and two light chains, joined by disulfide links.
- Fc Region: The "trunk" of the Y. This region triggers complement activation,
phagocytosis, and antibody-dependent cell-mediated cytotoxicity.
- Constant Region: Includes the trunk of the Y and the lower portion of each arm of the Y. This region is constant across all antibodies within an antibody class.
- Fab Region: The "arms" of the Y.
- Variable Region: Located at the far end of the Fab region, contains the antigen binding site.
The Fab region is Fabulous for Antigen Binding!
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Innate Immunity
Inflammation
Fever
Answer
Innate Immunity
Inflammation: Body's protective reaction to injury, disease, or irritation of the tissues. Characterized by redness/rubor, swelling, heat, pain, and altered function.
- First Stage: Tissue damage briefly causes vasoconstriction to minimize blood loss. Mast cells release cytokines (e.g., histamine), which triggers vasodilation in the local arterioles and ↑ vascular permeability in the capillaries.
- Second Stage: Phagocytes migrate to the area and kill the microorganisms. Exudate containing dead neutrophils and tissue cells (i.e., pus) may accumulate at the site.
- Third Stage: Damaged tissue is repaired or replaced by scar tissue.
Fever: Increase in body temperature due to release of exogenous or endogenous pyrogens that alter the 'thermostat setting' of the hypothalamus. Intensifies the body's immune response by stimulating leukocytes to kill pathogens. Fever also inhibits the growth of many pathogens.
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Innate Immunity: Phagocytosis
Pathogen Recognition
Steps in Phagocytosis
Answer
Innate Immunity: Phagocytosis
Process in which pathogens are engulfed and digested.
Pathogen Recognition: Pattern recognition receptors (PRRs) such as toll-like receptors (TLRs) on the phagocyte bind to pathogen-associated molecular patterns (PAMPs) on the pathogen, activating the phagocyte.
Steps in Phagocytosis:
- Chemotaxis (e.g., cytokines) attracts the phagocyte to the pathogen.
- Phagocyte forms a pseudopod that wraps around the pathogen.
- Pathogen becomes enclosed in an intracellular vesicle (i.e., phagosome).
- Phagosome fuses with a lysosome, forming a phagolysosome, and digestive enzymes from the lysosome kill and digest the pathogen.
- Digested material is either discharged from the cell via exocytosis or displayed on the cell surface (depending on the phagocyte).
Innate Immunity: Cellular Defenses
Granulocytes:
- Neutrophils: Most common leukocytes, first line of defense. Phagocytic, effective against bacterial infections.
- Eosinophils: Phagocytic, effective against parasitic infections.
- Basophils: Important in allergic reactions and other inflammatory responses.
Agranulocytes:
- Natural Killer Cells: Lymphocytes that recognize and destroy cells that are abnormal in some way. Release perforins to create temporary pores in the target cell membrane, allowing granzymes to enter the cell and initiate apoptosis (i.e., cell suicide).
- Monocytes: Upon leaving the bloodstream into the body tissues, differentiate to become macrophages or dendritic cells. Destroy pathogens through phagocytosis.
Macrophages and dendritic cells also serve as antigen-presenting cells and produce cytokines, which trigger adaptive immunity.
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Innate Immunity: Complement System
Complement Activation
Result of Complement Activation
Answer
Innate Immunity: Complement System
Serum proteins that activate one another in a cascade to help fight an infection. Triggers inflammation, facilitates phagocytosis, and damages bacterial cell membranes leading to cell lysis.
Complement Activation:
- Classical Pathway: Binding of antibody to the pathogen, forming an antibody-antigen complex.
- Alternative Pathway: Binding of complement proteins to lipopolysaccharides on the pathogen.
- Lectin Pathway: Binding of lectin (an acute phase protein) to carbohydrates on the pathogen surface.
Result of Complement Activation: Each of the above pathways lead into the common pathway, which activates C3 protein and triggers the rest of the complement cascade. This results in opsonization, inflammation, and formation of a membrane attack complex (MAC).
Innate Immunity: Physical Defenses
Physical Barriers: Skin, mucous membranes, endothelia, hair, eyelashes.
- Skin: Blocks pathogens from entering the deeper tissue.
- Keratin makes the skin surface tough, waterproof, and resistant to many bacterial enzymes.
- Adhered pathogens are removed with shedding of dead skin cells.
- Mucous Membranes: Line nasal and oral cavities, lungs, urinary tract, digestive tract, and reproductive tract.
- Secrete mucus, which protects underlying cells and traps pathogens.
- In the respiratory tract, cilia sweep mucus and debris towards the pharynx via the mucociliary escalator, where they can be coughed/sneezed out or swallowed.
Mechanical Defenses: Shedding of skin cells, mucociliary escalator, coughing and sneezing, peristalsis (i.e., muscular contractions in the digestive tract), flushing of body fluids (e.g., urination, tears).
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Toxins
Endotoxin
Exotoxin
Mycotoxin
Answer
Toxins
Endotoxin: Lipid A component of lipopolysaccharides in the outer membrane of Gram- negative bacteria.
- Released with bacterial cell death, triggers a general systemic inflammatory response in the host.
- Body does not produce effective antibodies to endotoxins.
Exotoxin: Protein molecules released by certain bacteria, primarily Gram-positive bacteria.
- Highly toxic, targets specific host cells. Bacterial cell death is not required for release.
- Includes intracellular targeting toxins (A-B toxins), membrane-disrupting toxins, and superantigens.
- Body produces antibodies called antitoxins in response to exotoxins.
Endotoxins are only lethal at very high concentrations, whereas exotoxins may be lethal at very small concentrations.
Mycotoxin: Toxin produced by a fungus (e.g., ergot toxin, aflatoxin).
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Microbiome
Normal (Resident) Microbiota
Transient Microbiota
Answer
Microbiome
Normal (Resident) Microbiota: Microbes that reside more or less permanently in or on a host, in a specific region. Do not cause disease under normal conditions.
- Diversity: Due to differences in physical and chemical factors (e.g., temperature, pH), different species of resident microbiota will live in or on different parts of the body.
- Benefits: Resident microbiota occupy space and utilize nutrients, outcompeting potential pathogens for these resources (i.e., microbial antagonism). They may also produce substances that kill/inhibit pathogens.
Transient Microbiota: Microbes that can be found temporarily in or on the host, in a specific region.
Opportunistic infections can be caused by transient microbes or microbes found in a different region than they normally reside.
Resident microbiota resides in the community while transient microbiota takes public transit outta there!
Disease Transmission
Vehicle Transmission: Transmission of a pathogen via non-living objects.
- Airborne Transmission: Transmission of a pathogen via infectious particles suspended in air for an extended period of time (e.g., measles).
- Waterborne Transmission: Transmission of a pathogen via contaminated water (e.g., cholera).
- Foodborne Transmission: Transmission of a pathogen via contaminated foods (e.g. listeriosis).
Vector Transmission: Transmission of a pathogen from one host to another by a living organism.
- Mechanical Vector: Organism carries the pathogen externally from one host to another without being infected itself (e.g., flies).
- Biological Vector: Pathogen reproduces within an organism that transmits the pathogen from one host to another (e.g., ticks).
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Disease Transmission
Direct Contact Transmission
Droplet Transmission
Indirect Contact Transmission
Answer
Disease Transmission
How an infectious agent is transmitted from its reservoir to a susceptible host.
Direct Contact Transmission: Physical contact (e.g., kissing, touching) allows for transmission of a pathogen between an infected person and susceptible person.
- Vertical: Transmission to a fetus or infant during pregnancy, birth, or breastfeeding.
- Horizontal: All other forms of direct contact transmission.
Droplet Transmission: Transmission of a pathogen occurs via respiratory droplets (e.g., coughing, sneezing) within a 1 meter distance.
Indirect Contact Transmission: Inanimate, contaminated object (i.e., fomite) involved in transmission of a pathogen (e.g., doorknob).
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Disease Transmission: Reservoir
Human
Animal
Nonliving
Answer
Disease Transmission: Reservoir
Where a pathogen normally lives, grows, and multiplies.
Human: Reservoir for many infectious diseases. A carrier is an individual capable of transmitting a pathogen without displaying symptoms of a disease (e.g., herpes simplex virus is often transmitted by asymptomatic carriers).
Animal: In zoonotic diseases, animals act as reservoirs of human disease (e.g., rabies, Lyme disease).
Nonliving: Environmental reservoirs, such as soil or water (e.g., Clostridium tetani resides in the soil).
Infection Terminology
Local Infection: Confined to a small area of the body, typically near the portal of entry (e.g., athlete's foot).
Focal Infection: Local infection spreads to a secondary location.
Systemic Infection: Infection becomes disseminated throughout the body.
Primary Infection: Initial infection caused by a pathogen.
Secondary Infection:
- Decreased immune function from the primary infection leads to infection by another pathogen (e.g., HIV infection makes the patient susceptible to opportunistic infections such as pneumonia).
- May also result from treatment of the primary infection (e.g., antibiotics impair the normal microbiota, allowing for an opportunistic infection).
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Stages of Pathogenesis
Exposure
Adhesion
Invasion
Infection
Answer
Stages of Pathogenesis
Exposure: Pathogen enters a susceptible host through a portal of entry (e.g., skin, mucosal membranes, parenteral route).
Adhesion: Attachment of a pathogen to a host cell. Adhesins are molecules on the surface of pathogens that bind to receptors on the host cell.
Invasion: Spread of the pathogen in a localized area or the entire body.
Infection: Multiplication of the pathogen, leading to a local, focal, or systemic infection.
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Types of Disease
Acute Disease
Chronic Disease
Latent Disease
Answer
Types of Disease
Acute Disease: Disease develops rapidly over a short period of time, such as hours, days, or weeks (e.g., influenza).
Chronic Disease: Disease develops more slowly over a longer period of time, such as months, years, or a lifetime (e.g., hepatitis C).
Latent Disease: Disease in which the pathogen becomes dormant but may be reactivated to cause an active infection (e.g., herpes simplex virus).
Card 176
Periods of an Infectious Disease
Illustration
Answer
Periods of an Infectious Disease
Card 177
Periods of an Infectious Disease
Incubation Period
Prodromal Period
Period of Illness
Period of Decline
Period of Convalescence
Answer
Periods of an Infectious Disease
Incubation Period: Period following entry of the infectious agent in the host. Infectious agent begins multiplying in the host. Signs and symptoms are not present.
Prodromal Period: Infectious agent continues to multiply. Host exhibits mild, non-specific signs and symptoms of the disease (i.e., fatigue, low- grade fever).
Period of Illness: Number of infectious agents increases sharply. Period characterized by severe, specific signs and symptoms of the disease (i.e., cough, nausea/vomiting).
Period of Decline: Number of infectious agents decreases sharply, signs and symptoms decrease.
Period of Convalescence: Infectious agent is eliminated. Signs and symptoms resolve, although some diseases may cause permanent damage.
Disease Terminology
Infectious Disease: Disease caused by a pathogen (e.g., bacteria, virus, fungus).
Noninfectious Disease: Disease not caused by a specific pathogen. Contributing factors include genetics, environment, and immune dysfunction.
Communicable Disease: Infectious disease spread from person to person via direct or indirect means.
Contagious Disease: Communicable disease that is easily spread.
Noncommunicable Disease: Infectious disease not spread from person to person (e.g., tetanus caused by C. tetani).
Iatrogenic Disease: Disease contracted as a result of a medical procedure (e.g., surgery) or medication.
Nosocomial Disease: Disease acquired in a hospital setting. Also known as HAI (healthcare-associated infection).
Zoonotic Disease: Infectious disease transmitted to humans from animals.
Disease Terminology
Infection: Colonization of a host by a pathogen (e.g., bacterium, virus, fungus) that results in multiplication of the pathogen and a response from the host's immune system.
Disease: Normal functions or structure of the host are impaired or damaged, causing signs and symptoms (i.e., disruption in homeostasis).
Signs: Objective, can be directly observed or measured by the clinician (e.g., fever).
Symptoms: Subjective, felt or experienced by the patient (e.g., pain).
Syndrome: Group of signs and symptoms that are characteristic of a particular condition.
Asymptomatic: Signs and symptoms of a disease are not present in the host.
Biological Safety Levels (BSLs)
Containment guidelines required to work with a biological agent in a laboratory.
BSL-1: Agent poses minimal risk (e.g., non-pathogenic E. coli). Standard aseptic technique used, personal protective equipment (PPE) as needed.
BSL-2: Agent poses moderate risk (e.g, S. aureus). Restricted access to lab, PPE required. Certain procedures performed in biological safety cabinet (BSC). Laboratory has an autoclave.
BSL-3: Agent poses threat of lethal infections through inhalation (e.g., M. tuberculosis). Restricted lab access with medical surveillance, PPE and respirators required, all procedures performed in BSC, directional airflow in lab.
BSL-4: Most dangerous, often fatal agents (e.g., Ebola virus). All BSL-3 precautions plus change clothing upon entry, shower and decontamination of all material upon exiting. Full body, positive pressure suit required. Lab with dedicated air supply and exhaust system.
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Testing Effectiveness of Antimicrobials
Kirby-Bauer Disk Diffusion Test
Dilution Test
Epsilometer (E-Test)
Answer
Testing Effectiveness of Antimicrobials
Kirby-Bauer Disk Diffusion Test: Determines the susceptibility of a microorganism to various antimicrobial drugs. Filter paper disks impregnated with known concentrations of antibacterial drugs are placed on an agar plate containing the isolated bacterial pathogen. Antibacterial activity is observed as a clear circular zone of inhibition around the impregnated disk.
This test does not differentiate between inhibition of bacterial growth (i.e., bacteriostatic) vs. killing of bacterial cells (i.e., bactericidal).
Dilution Test: Used to determine a drug's minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). MIC is the lowest drug concentration that inhibits visible bacterial growth. MBC is the lowest drug concentration that kills 99.9% of the starting inoculum.
E-Test: Alternate test for determining MIC that combines the Kirby-Bauer disk diffusion test with the dilution test.
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Multidrug-Resistant Microbes
MSRA
VRE
VRSA
VISA
ESBLs
CRE
MDR-TB
XDR-TB
Antibiotic Resistance
Drug Modification or Inactivation
Decreased Penetration
Efflux Pump
Target Modification
Answer
Antibiotic Resistance
Defenses developed by bacteria to evade the effect of antibiotics. Contributing factors: overuse or misuse of antibiotics, subtherapeutic dosing, patient non-compliance with treatment plan.
Drug Modification or Inactivation: Microbial enzyme chemically modifies or destroys an antimicrobial, so it is unable to reach its target.
Decreased Penetration: Mechanisms that prevent a drug from reaching its target (e.g., decrease in number of porins in the outer membrane).
Efflux Pump: Mechanism that actively transports antimicrobial drugs out of the cell.
Target Modification: Structural changes to target sites to prevent drug binding (e.g., alteration of the binding site, or creation of a "bypass" to eliminate dependence on the target).
Card 184
Superinfection
Illustration
Answer
Superinfection
A secondary (opportunistic) infection in a patient with a preexisting infection.
Antimicrobial Drugs
Antifungal Medications: Most interfere with ergosterol synthesis or bind to ergosterol to disrupt fungal cell membrane integrity. Selectively toxic, as human cell membranes use cholesterol vs. ergosterol.
- Examples: Miconazole, ketoconazole, clotrimazole, fluconazole, nystatin, amphotericin B.
Antiviral Medications: Inhibit viral entry, inhibit viral uncoating, inhibit nucleic acid biosynthesis, prevent viral escape from endosomes in host cells, or prevent viral release from infected cells.
- Examples: Acyclovir, ribavirin, amantadine, oseltamivir, azidothymidine/ zidovudine (AZT), nirmatrelvir (Paxlovid).
Because HIV can easily mutate to become drug resistant, treatment requires a combination of several antiretroviral drugs (ART = Antiretroviral therapy).
Antimicrobial Drugs
Antiprotozoal Medications: Mode of action varies across antiprotozoal agents. Used to treat protozoan infections such as malaria, toxoplasmosis, and giardiasis.
- Examples: Metronidazole, sulfadiazine, chloroquine, artemisinin-based combination therapy (ACT).
Antihelminthic Medications: Mode of action varies across anthelmintic agents. Used to treat infections such as roundworm and tapeworm infections.
- Examples: Albendozole, ivermectin, niclosamide.
Antimicrobial Drugs: Metabolic Pathway Inhibitors
Antibiotics that disrupt the synthesis of essential metabolites (e.g., vitamins).
Sulfonamides: Block synthesis of folic acid required for nucleic acid synthesis. Also used in combination with other antimicrobials to treat malaria and toxoplasmosis. Allergic reactions to sulfa drugs are common. Bacteriostatic, broad spectrum (e.g., sulfamethoxazole, trimethoprim).
Isoniazid: Prevents synthesis of mycolic acid. Specific toxicity for mycobacteria. Used in combination with rifampin or streptomycin to treat tuberculosis. Bactericidal, narrow spectrum.
Card 188
Antimicrobial Drugs: Membrane Function Inhibitors
Polymyxins
Lipopeptides
Answer
Antimicrobial Drugs: Membrane Function Inhibitors
Antibiotics that alter membrane permeability in bacteria.
Polymyxins: Interact with lipopolysaccharides in the outer membrane of Gram-negative bacteria, disrupting the inner and outer membrane. Bactericidal, narrow spectrum (e.g., polymyxin B, colistin).
Lipopeptides: Insert into the cytoplasmic membrane of Gram-positive bacteria, causing rapid depolarization of membrane potential. Bactericidal, broad or narrow spectrum (e.g., daptomycin).
Antimicrobial Drugs:
Nucleic Acid Synthesis Inhibitors
Antibiotics that interfere with DNA replication or transcription in microorganisms.
Nitroimidazoles: Interfere with DNA replication in target cells. Treat anaerobic bacterial and protozoal infections. Bactericidal, broad spectrum (e.g., metronidazole).
Rifamycins: Block RNA polymerase activity in bacteria. Primarily used against mycobacteria that cause tuberculosis. Bactericidal, narrow spectrum (e.g., rifampin).
Fluoroquinolones: Inhibit DNA gyrase activity. Used for a wide variety of skin and systemic infections. Bactericidal, broad spectrum (e.g., ciprofloxacin, levofloxacin).
Card 190
Antimicrobial Drugs: Protein Synthesis Inhibitors
Aminoglycosides
Tetracyclines
Macrolides
Lincosamides
Answer
Antimicrobial Drugs: Protein Synthesis Inhibitors
Antibiotics that target 70S ribosomes (unique to bacterial cells), which interferes with translation of mRNA into proteins.
Aminoglycosides: Bind to the 30S subunit of ribosomes, resulting in mRNA misreading and production of faulty proteins. Bactericidal, broad spectrum (e.g., gentamicin, neomycin, streptomycin).
Tetracyclines: Block tRNA from binding with the ribosome during translation. Bacteriostatic, broad spectrum (e.g., doxycycline).
Macrolides: Bind to the 50S subunit of ribosomes, prevents peptide bond formation. Bacteriostatic, broad spectrum (e.g., erythromycin, azithromycin).
Lincosamides: Bind to the 50S subunit of ribosomes, prevents peptide bond formation. Bacteriostatic or bactericidal at high concentrations, narrow spectrum (e.g., clindamycin).
Antimicrobial Drugs: Cell Wall Inhibitors
Antibiotics that prevent the synthesis of peptidoglycan in the bacterial cell wall, weakening the cell wall and causing cell lysis.
Penicillins: Contains a β-lactam ring, blocks crosslinking of peptide chains during synthesis of peptidoglycan. Bactericidal, broad or narrow spectrum (e.g., amoxicillin).
Cephalosporins: β-lactam antibiotic, chemical structure increases its resistance to enzymatic inactivation by bacterial β-lactamases. Bactericidal, broad spectrum (e.g., cephalexin).
Monobactams: β-lactam ring is not fused to any other ring. Bactericidal, broad or narrow spectrum (e.g., aztreonam).
Carbapenems: β-lactam antibiotic. Bactericidal, broad spectrum (e.g., imipenem).
Polypeptide Antibiotics: Prevents cell wall subunits from being incorporated into peptidoglycan. Bactericidal, broad or narrow spectrum (e.g., vancomycin, bacitracin).
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Antimicrobial Drug Terminology
Dosage
Route of Administration
Synergism
Antagonism
Answer
Antimicrobial Drug Terminology
Dosage: Amount of medication given during a certain time interval.
Route of Administration: How a drug is introduced into the body (e.g., oral, intravenous).
Synergism: Two or more drugs used in combination to provide an effect that is better than the efficacy of either drug alone.
Antagonism: The use of two or more drugs that produces a harmful effect (e.g., decreased drug effectiveness, toxicity).
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Antimicrobial Drug Terminology
Selective Toxicity
Bactericidal
Bacteriostatic
Mode of Action
Narrow-Spectrum
Broad-Spectrum
Answer
Antimicrobial Drug Terminology
Selective Toxicity: The ability of an antimicrobial drug to selectively kill or inhibit microbial growth while causing minimal or no harm to the host.
Bactericidal: Antimicrobial drug that kills bacteria.
Bacteriostatic: Antimicrobial drug that inhibits bacterial growth.
Mode of Action: The way in which a drug affects microbes at the cellular level (i.e., inhibition of cell wall synthesis).
Narrow-Spectrum: Antimicrobials that target specific subsets of bacterial pathogens. Used when the causative agent is known.
Broad-Spectrum: Antimicrobials that target a wide variety of bacterial pathogens. Used when the causative agent is not known.
Card 194
Evaluation of Disinfectants
Use-Dilution Test
Disk Diffusion Method
Answer
Evaluation of Disinfectants
Use-Dilution Test: Determines the effectiveness of a disinfectant on an inanimate surface.
- Cylinders are dipped into a culture of the microorganism and allowed to dry.
- Each cylinder is then dipped into decreasing concentrations of the disinfectant and are transferred to new test tubes with fresh sterile media.
- Test tubes are incubated, and bacterial survival is indicated by the presence of turbidity.
Disk Diffusion Method: Tests the susceptibility of specific microorganisms to chemicals or antimicrobial drugs.
- Filter paper disks are soaked with different chemicals and placed on an agar plate that has been inoculated with the target bacterium.
- If a chemical is effective, a zone of inhibition is observed as a clear area around the disk. The larger the zone the more effective the agent is.
Card 195
Chemical Methods
Bisbiguanides
Alkylating Agents
Peroxygens
Supercritical Fluids
Chemical Food Preservatives
Answer
Chemical Methods
Bisbiguanides: Topical antiseptics that disrupts cell membranes. Often used for surgical hand scrubbing and patient skin preparation (e.g., chlorhexidine).
Alkylating Agents: Strong disinfecting chemicals that inactivate enzymes and nucleic acids (e.g., formaldehyde, glutaraldehyde).
Peroxygens: Strong oxidizing agents that produce free radicals and damage cellular macromolecules. Used as disinfectants (e.g., hydrogen peroxide, benzoyl peroxide, ozone gas).
Supercritical Fluids: Penetrate cell, lowering cell pH. Used to treat foods and medical devices (e.g., supercritical carbon dioxide).
Chemical Food Preservatives: Food additives that inhibit microbial growth and minimize spoilage (e.g., sorbic acid, nitrites).
Card 196
Chemical Methods
Phenolics
Heavy Metals
Halogens
Alcohols
Surfactants
Answer
Chemical Methods
Phenolics: Denature proteins and disrupt membranes. Used in household cleaners, mouthwash, antibacterial hand soaps.
Heavy Metals: Denature proteins and inhibit enzymatic activity (e.g., silver, mercury, nickel, copper, zinc).
Halogens: Oxidizes and destabilizes cellular macromolecules. Chlorine is used for water disinfection, iodine is an effective antiseptic.
Alcohols: Rapidly denature proteins, inhibit cell metabolism, and alter membrane permeability leading to cell lysis. Not effective against endospores or nonenveloped viruses. Used in hand sanitizer and rubbing alcohol. Typically used at 70% concentration in aqueous solution.
Surfactants: Group of chemical compounds that lower the surface tension of water. Loosen and lift away dirt and microbes from surfaces and skin, degerm surfaces. Used in soaps and detergents.
Physical Methods
Ionizing Radiation:
- Use of short wavelength, high intensity radiation (e.g., X-rays, gamma rays).
- Leads to breaks in DNA strands.
- Used for sterilization of medical supplies and food preservation.
- Penetrates paper, plastics, wood, metal, tissues.
Non-Ionizing Radiation:
- Uses longer wavelength, lower intensity radiation (e.g., UV light).
- Forms thymine dimers, which inhibit DNA replication and transcription.
- Used for water purification and surface sterilization of laboratory materials.
- Does not penetrate surfaces, including plastics and glass.
Card 198
Physical Methods
Refrigeration/Freezing
High Pressure
Desiccation
Osmotic Pressure
Filtration
Answer
Physical Methods
Refrigeration/Freezing: Temperatures of 0 - 7°C have a bacteriostatic effect (i.e., slows microbial growth). Temperatures below -2°F kill some organisms, but psychrophilic bacteria may survive.
High Pressure: Nonthermal process used to kill microbes in food products, extending shelf life while maintaining food quality.
Desiccation: Use of drying/dehydration to control microbial growth and preserve foods (e.g., lyophilization, also known as freeze-drying).
Osmotic Pressure: The addition of salt or sugar to create a hypertonic environment, which causes water to leave the microbial cells. Used to preserve foods (e.g., cured meats, jams).
Filtration: Physical separation of microbes by passing the sample through a filter with small pores. Used to filter air (e.g., HEPA filter) or a liquid (e.g., membrane filter).
Physical Methods
Dry Heat Sterilization: Direct application of high heat (e.g., direct flaming of inoculating loops, incineration).
Moist Heat Sterilization:
- Boiling: Kills vegetative cells and some viruses. Best suited for personal use (e.g., sanitizing baby bottles).
- Autoclave: Application of steam under pressure. Achieves a higher temperature than boiling. Used for sterilization of medical/lab supplies. Kills all microbes, including endospores.
Pasteurization: Treatment of food products (e.g., milk, juice) with mild heat to remove disease and spoilage-causing microbes without ruining the taste or consistency of the food.
Thermal death point represents the lowest temperature at which cells in a culture are killed in 10 minutes. Thermal death time represents the time needed to kill all cells at a specific temperature.
Card 200
Microbial Control
Key Factors Impacting Treatment Effectiveness
Decimal Reduction Time (DRT)
Actions of Microbial Control Agents
Answer
Microbial Control
Key Factors Impacting Treatment Effectiveness:
- Number of microbes.
- Environmental factors (e.g., temperature, nutrient levels, biofilms).
- Time of exposure to microbial control agent.
- Microbial characteristics (e.g., cell wall composition, available enzymes).
Decimal Reduction Time (DRT): Amount of time required for a specific chemical compound to kill off 90% of the population of a microbial species. Bacteria typically die at a constant rate, linear when plotted logarithmically.
Actions of Microbial Control Agents:
- Increase membrane permeability (e.g., damage to lipid bilayer).
- Damage to proteins (e.g., disruption to protein structure).
- Damage to nucleic acids (e.g., impairment of replication or metabolism).
Card 201
Microbial Control Terminology
Sterilization
Commercial Sterilization
Disinfection
Antisepsis
Sanitization
Degerming
Answer
Microbial Control Terminology
Sterilization: The destruction or removal of all microorganisms, including vegetative cells, endospores, and viruses.
Commercial Sterilization: Use of limited heat to destroy microbes responsible for foodborne illnesses, but preserves food quality. Destroys C. botulinum endospores. Does not kill thermophilic bacteria.
Disinfection: Destruction of microorganisms, but not endospores, on a surface using antimicrobial chemicals or heat.
Antisepsis: Application of an antimicrobial chemical on living tissue (e.g., isopropyl alcohol).
Sanitization: Treatment that reduces microbial load on inanimate surfaces.
Degerming: Reduction of microbes by using a mild chemical and mechanical removal with gentle scrubbing (e.g., washing hands with soap).
Card 202
Other Acellular Infectious Agents
Viroid
Prion
Answer
Other Acellular Infectious Agents
Viroid: Consists of a short strand of circular RNA, no protein coat. Only pathogenic towards plants.
Prion: Infectious, misfolded protein that causes abnormal folding of other proteins, forming plaques. Causes transmissible spongiform encephalopathy (TSE), which leads to degeneration of brain tissue in humans and animals (e.g., Creutzfeldt-Jakob disease, kuru).
Prions are resistant to chemicals, heat, and radiation. No treatment or cure is available for TSE.
Card 203
Cultivation & Identification of Viruses
Bacteriophages
Animal Viruses
Answer
Cultivation & Identification of Viruses
Bacteriophages: Inoculated to a bacterial lawn. Presence of clear areas on the lawn correlate to regions of lysed bacteria (i.e., plaques).
Animal Viruses: Cultivation requires some form of a host cell (e.g., whole organism, embryo, or cell culture). Viruses are detected through a number of methods.
- Cytopathic Effects: Distinct, observable cell abnormalities due to a viral infection.
- Serological Assays: Virus is identified based on its reaction with antibodies (e.g., hemagglutination assay, enzyme-linked immunosorbent assay).
- Nucleic Acid Amplification Tests: Detects unique nucleic acid sequences of viruses in patient samples (e.g., polymerase chain reaction).
Viral Growth Curve
Inoculation: Virions attach to the host cells.
Eclipse Phase: Virions enter the host cells and are no longer detectable in the medium (or extracellular fluid of the host).
Burst: Virions are released from the lysed host cells at the same time.
Burst Size: The number of virions released per infected host cell.
Viral Titer: Concentration of viral particles (i.e., number of virions in the medium per unit volume).
Viral Infections
Persistent Viral Infection: Virus stays in the tissues/organs of the infected individual, causing a latent or chronic infection.
Latent Viral Infection: Virus remains dormant or hidden in cells with no viral replication. Virus is either outside of the host chromosomes or integrated into a chromosome as a provirus.
- Examples: Varicella-zoster virus, herpes simplex virus.
Latent viruses may be reactivated after years of dormancy.
Chronic Viral Infection: Symptoms are recurrent or persistent over a long time with active viral replication. May occur after a long period of latency.
- Examples: Hep C, HIV.
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Viral Replication
Double-Stranded DNA Virus (dsDNA)
Single-Stranded DNA Virus (ssDNA)
Retrovirus
Answer
Viral Replication
dsDNA: Host enzymes can be used for viral genome replication and protein production.
ssDNA: Host enzymes are used to synthesize a complementary strand, producing dsDNA, which can then be replicated and transcribed.
Retrovirus:
- Viral genome consists of two identical copies of +ssRNA.
- The virus carries reverse transcriptase, an enzyme that synthesizes dsDNA from the +ssRNA. It also degrades the original viral RNA.
- The dsDNA becomes integrated into the host chromosome by viral integrase, forming a provirus.
- Expression of the provirus allows viral RNA and viral proteins to be synthesized. A new, immature virus forms from the assembly of viral particles.
- The newly formed virus is released and produces protease, which breaks up proteins in the immature virus to create the mature virus.
Viral Replication
+ssRNA: Also referred to as sense or positive strand.
- Viral RNA acts as mRNA and is translated directly to make viral proteins.
- In order to replicate the viral genome, viral RNA-dependent RNA polymerase (RdRP) is used to synthesize a complementary strand (i.e., negative strand) to serve as a template to synthesize more positive strands.
-ssRNA: Also referred to as anti-sense or negative strand.
- Viral RNA cannot be directly used for translation to make viral proteins.
- RdRP uses the negative strand as a template to synthesize a complementary strand (i.e., positive strand). This complementary strand can be translated to make viral proteins and serves as a template to synthesize more negative strands.
dsRNA virus: Contains both a positive and negative strand. RdRP is used to make copies of both strands for replication of the dsRNA genome.
Card 209
Viral Replication: Animal Hosts
Illustration
Answer
Viral Replication: Animal Hosts
Card 210
Viral Replication: Animal Hosts
Steps
Answer
Viral Replication: Animal Hosts
Attachment: The virus binds to the host cell.
Entry: Virus enters the host cell through endocytosis, membrane fusion, or other method. Enveloped viruses enter via membrane fusion, whereas non-enveloped viruses enter via endocytosis.
Uncoating: Removal of capsid proteins, release of viral contents (e.g., genetic material, enzymes).
Biosynthesis: Synthesis of viral proteins and replication of the viral genome. Occurs in the nucleus or cytoplasm of the host cell.
Assembly: Viral components are assembled.
Release: The new virus is released from the host cell via exocytosis, budding, or rupture of the host cell. Many enveloped viruses are released by budding. Many non-enveloped viruses are released by rupturing the cell.
Viral Replication: Transduction
Transfer of bacterial DNA from one bacterium to another by a bacteriophage.
Generalized Transduction: During the lytic cycle, a random piece of host DNA is inserted into the capsid. After release of the new virus, this DNA is then injected into a new host cell.
Specialized Transduction: During the lysogenic cycle, when the phage DNA is excised from the host chromosome, adjacent bacterial genes on either side of the phage DNA remain attached. This DNA is then injected into a new host cell.
Transduction is a mechanism of horizontal gene transfer that introduces genetic diversity.
Viral Replication: Lysogenic Cycle
Method of viral replication where a bacteriophage genome becomes integrated into the host's chromosome through lysogeny.
Attachment: The virus attaches to the host surface.
Penetration: The viral genome is injected into the host cell. Capsid remains outside the cell.
Integration: Phage DNA inserts itself into the host chromosome, forming an integrated genome called a prophage.
Cell Division: Phage DNA and bacterial DNA is replicated and passed on to new daughter cells.
Induction, which may be triggered by an environmental stressor (e.g., starvation, exposure to chemicals), causes the phage genome to be excised from the bacterial chromosome and initiation of the lytic cycle.
Card 215
Viral Replication: Lytic Cycle
Illustration
Answer
Viral Replication: Lytic Cycle
Card 216
Viral Replication: Lytic Cycle
Steps
Answer
Viral Replication: Lytic Cycle
Method of viral replication where a bacteriophage takes over a cell, reproduces new phages, and destroys the cell.
- Attachment: The virus attaches to the host surface.
- Penetration: The viral genome is injected into the host cell. The capsid remains outside the cell.
- Biosynthesis: The phage takes over the host cell's machinery to make viral components.
- Maturation: New viral components are assembled.
- Release: The cell lyses and releases the new phages.
Card 217
Virus Shapes & Structures
Illustration
Answer
Virus Shapes & Structures
Card 218
Virus Shapes
Helical
Polyhedral
Complex
Answer
Virus Shapes
Helical: Cylindrical or rod-shaped capsid, with the viral nucleic acid coiled inside the length of the capsid.
Polyhedral: A nucleic acid surrounded by a multi-sided capsid. A icosahedron is a 20-sided structure, which appears spherical in shape.
Helical or polyhedral viruses may have envelopes.
Complex: The capsid contains features of both helical and polyhedral viruses (e.g., bacteriophage).
Card 219
Virus Components
Genetic Material
Capsid
Envelope
Spikes
Answer
Virus Components
Genetic Material: Consists of DNA or RNA, but not both.
Capsid: A protein coat that surrounds and protects the nucleic acid. Composed of capsomeres (i.e., protein subunits) that interlock to form the capsid.
Envelope: The phospholipid membrane layer that surrounds most viruses, derived from the host cell. A virus lacking an envelope is known as a non-enveloped or naked virus.
Spikes: Protein structures extending outward and away from some viruses. Allow viruses to attach and enter the cell and detach during release from cell.
Card 220
Virus
Size
Host Range
Bacteriophage
Virion
Answer
Virus
Acellular pathogen (i.e., not composed of or containing cells).
Viruses are obligate intracellular parasites. They require a host cell to survive and reproduce.
Size: 20 nm to 900 nm in length.
Host Range: Describes the range of cell types and host species a virus is able to infect.
Bacteriophage: Virus that infects a bacterium. Referred to as a "phage".
- Virulent Phage: Causes death of the cell through cell lysis.
- Temperate Phage: Becomes part of the host chromosome and is replicated with cell division.
Virion: Complete virus particle outside of the host cell (i.e., released from the virus-infected host cell).
Polymerase Chain Reaction (PCR)
A molecular technique used to rapidly amplify the number of copies of a target DNA sequence using an instrument called a thermal cycler.
Applications: Genotyping, cloning, forensics, paternity testing, identification of microorganisms, mutagenesis, ancient DNA analysis.
Reagents: Target DNA template, Taq DNA polymerase (isolated from the thermophilic bacterium Thermus aquaticus), forward and reverse DNA primers, deoxynucleotide triphosphates (dNTPs).
Steps:
- Denaturation: Temperature raised to ~ 95°C to separate the double- stranded DNA into single-stranded DNA.
- Annealing: Temperature lowered to ~ 50°C, which allows DNA primers to attach or anneal to the ends of the target sequence.
- Extension: Temperature raised to ~72°C, which allows Taq DNA polymerase to synthesize a complementary strand of DNA.
Each cycle doubles the # of DNA copies. Cycle is repeated ~ 30 times.
Card 223
Tools of Genetic Engineering
CRISPR
DNA Probe
Answer
Tools of Genetic Engineering
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats): A gene editing technique that allows scientists to make specific, targeted changes in DNA. Derived from an adaptive defense system found in bacteria.
- Applications: Research (e.g., study how a mutation affects gene expression), treatment of diseases (e.g., genetic conditions, cancer), agriculture (e.g., development of improved crops).
DNA Probe: A single-stranded DNA fragment used to identify a gene of interest in a clinical sample. The fragment is complementary to the gene of interest, and is tagged with a radioactive atom or fluorescent dye.
- Applications: Research (e.g., study where certain mRNAs are expressed in a cell), diagnosis of diseases (e.g., confirm presence of pathogen in a patient sample).
Card 224
Agarose Gel Electrophoresis
Illustration
Answer
Agarose Gel Electrophoresis
Card 225
Agarose Gel Electrophoresis
Key Points/Steps
Answer
Agarose Gel Electrophoresis
A technique used to separate DNA fragments by size.
Key Points/Steps:
- DNA and RNA are negatively charged molecules.
- DNA/RNA samples are placed in the wells of the gel, located at the negative end of the gel. One well, called a DNA ladder, contains DNA fragments of known sizes.
- An electrical current causes molecules to move from the negative end of the gel towards the positive end of the gel.
- Smaller molecules travel faster across the gel.
- Adding a stain (e.g., ethidium bromide) allows fragments to be visualized. DNA fragments of the same size form bands in the gel. The sample bands can be compared to bands of known size in the DNA ladder.
The distance the fragment migrates is inversely correlated to the size of the fragment.
Blue-White Screening
Efficient method for identifying recombinant bacteria in vector-based experiments.
Selectable Markers:
- Antibiotic resistance gene to differentiate bacteria that have taken up the plasmid.
- LacZ gene to differentiate bacteria with the plasmid containing the gene of interest (vs. the plasmid alone).
Key Points/Steps:
- Foreign DNA is inserted into the lacZ gene of the plasmid vector, disabling the gene.
- If the bacterium incorporates the plasmid vector with the foreign DNA, the lacZ gene is interrupted. The bacterium will not break down X-gal (an analog to galactose) in the medium. White colonies are produced.
- If the bacterium does not incorporate the plasmid vector with the foreign DNA (i.e., the plasmid re-anneals to itself and has an intact lacZ gene), the bacterium will break down X-gal in the medium. Blue colonies are produced.
Card 227
Vectors
Plasmid Requirements
Answer
Vectors
DNA molecules (e.g., plasmids) used as a vehicle to transfer specific DNA sequences into a host cell.
Plasmid Requirements:
- Origin of Replication: Site on the plasmid where DNA replication begins.
- Multiple Cloning Site (MCS): Short sequence of DNA on the plasmid that contains restriction enzyme sites, allowing a piece of DNA to be inserted into that region.
- Selectable Marker: Gene on the plasmid that allow researchers to determine if the host cell has taken up the vector (e.g., genes that encode for antibiotic resistance).
Card 228
Recombinant DNA Technology
Illustration
Answer
Recombinant DNA Technology
Card 229
Restriction Enzymes
Illustration
Answer
Restriction Enzymes
Card 230
Tools of Genetic Engineering
Molecular Cloning
Restriction Enzymes
Answer
Tools of Genetic Engineering
Molecular Cloning: Introduction of recombinant DNA into an easily manipulated host, resulting in the production of multiple identical copies of the gene of interest.
Restriction Enzymes: Bacterial enzymes used in recombinant DNA technology. Cut DNA at specific, often palindromic, recognition sites.
- Restriction enzymes can make a staggered cut, producing sticky ends (i.e. molecules with complementary overhangs) or a straight cut, producing blunt ends (i.e., molecules without overhangs).
- DNA ligase joins 2 DNA pieces through covalent bonding.
Restriction enzymes are referred to as 'molecular scissors'.
Card 231
Biotechnology
Genetic Engineering
Recombinant DNA Technology
Transgenic
Applications of Biotechnology
Answer
Biotechnology
The branch of applied science that manipulates cellular and biomolecular processes to benefit humankind.
Genetic Engineering: Modification of an organism's genome to achieve desirable traits.
Recombinant DNA Technology: The process of manipulating DNA sequences in vitro (i.e., outside of a living organism), creating novel DNA combinations.
Transgenic: An organism in which DNA from a different species has been introduced.
Applications of Biotechnology:
- Therapeutic Applications: Production of insulin, human growth hormone, interferon, Hepatitis B vaccine, gene therapies.
- Agricultural Applications: Pest-resistant crops, herbicide-resistant crops, golden rice (i.e., rice that contains beta-carotene).
- Industrial Applications: Craft brewing, textiles, biofuels.
- Forensics: DNA analysis and fingerprinting.
Card 232
Lac Operon
Illustration
Answer
Lac Operon
Card 233
Inducible Operons
Lac Operon
Answer
Inducible Operons
Genes are only transcribed in the presence of an inducer. Usually "off", but can be turned "on".
Lac Operon: Inducible operon that contains genes that code for enzymes involved in lactose metabolism. For transcription to occur, lactose must be present and glucose must be depleted.
- Lactose:
- When lactose is absent, lac repressor is bound to the operator site, blocking transcription.
- When lactose is present, allolactose binds the repressor, changing its shape so it can no longer bind to the operator, allowing for transcription.
- Glucose:
- When glucose levels are low, cAMP accumulates and binds to CAP. cAMP- CAP complexes bind to the promoter, which stimulates RNA polymerase activity and ↑ transcription.
- When glucose levels are high, there is ↓ cAMP. cAMP-CAP complexes do not form and cannot bind to the promoter. Transcription occurs at a low rate.
Card 234
Trp Operon
Illustration
Answer
Trp Operon
Card 235
Repressible Operons
Trp Operon
Answer
Repressible Operons
Genes are transcribed by default unless turned off by a repressor. Usually "on", but can be turned "off".
Trp Operon: Repressible operon that codes for enzymes needed to synthesize the amino acid tryptophan.
- When tryptophan is present, tryptophan binds to the trp repressor, which binds to the operator site, blocking transcription.
- When tryptophan is absent, the trp repressor dissociates from the operator, allowing for transcription.
Tryptophan is a co-repressor that activates the repressor.
Card 236
Gene Regulation: Operon Theory
Illustration
Answer
Gene Regulation: Operon Theory
Card 237
Gene Regulation: Operon Theory
Operon
Regulatory Gene
Activator
Repressor
Answer
Gene Regulation: Operon Theory
Operon: Related genes transcribed together and under the control of a single promoter. Contains a promoter site, operator site, and structural genes.
- Promoter: Site on the operon where RNA polymerase binds and initiates transcription.
- Operator: Site on the operon that binds the repressor molecule.
- Structural Genes: Site on the operon that codes for enzymes.
Regulatory Gene: DNA sequence that codes for proteins that control transcription of the operon.
Activator: Regulatory protein that facilitates binding of RNA polymerase to the promoter to increase transcription of a gene.
Repressor: Regulatory protein that binds at the operator site on the operon to block transcription of a gene.
Some operons are constitutively expressed (i.e., expressed continuously without regulation).
Transposons
Molecules of DNA (i.e., "jumping genes") that include inverted repeat sequences at their ends and a gene encoding for the enzyme transposase. This allows for a DNA sequence to be independently excised from one location and integrated into DNA at a different location.
Nonreplicative Transposons: Move genes in a "cut-and-paste" fashion, excising the genes from one location and moving them to another.
Replicative Transposons: Make a copy of genes to be inserted elsewhere, while retaining the original sequence at its current location.
Transposons may carry antibiotic resistance genes and move these genes from chromosomes to plasmids. Plasmids can then be easily transferred to other bacteria via conjugation.
Card 239
Conjugation
Illustration
Answer
Conjugation
Card 240
Conjugation
F Plasmid
Donor (F+) Cells
Recipient (F-) Cells
Conjugation of the F Plasmid
Answer
Conjugation
F Plasmid: Small, circular, double-stranded DNA molecule, located independent from the bacterial chromosome. Contains genes encoding the ability to conjugate.
Donor (F+) Cells: Bacterial cells that contain the F plasmid and are capable of forming an F pilus (i.e., conjugation pilus).
Recipient (F-) Cells: Bacterial cells lacking an F plasmid.
Conjugation of the F Plasmid:
- Pilus of donor cell attaches to the recipient cell. Pilus contracts, and cells are drawn together.
- Cytoplasmic bridge forms between the two cells.
- One strand of the double-stranded F plasmid is transferred from the donor cell (i.e., F+ cell) to the recipient cell (i.e., F- cell).
- Donor cell synthesizes a complementary strand to restore the plasmid. Recipient cell synthesizes a complementary strand for the plasmid and becomes an F+ cell with a pilus.
Plasmids often code for genes that increase a cell's virulence (e.g., antibiotic resistance, production of toxins).
Card 241
Horizontal Gene Transfer
Illustration
Answer
Horizontal Gene Transfer
Card 242
Horizontal Gene Transfer
Transformation
Transduction
Conjugation
Answer
Horizontal Gene Transfer
Movement of genetic information between organisms by mechanisms other than the vertical transfer from parent to offspring. Allows asexual prokaryotes to acquire new traits.
Transformation: DNA is released from other cells upon death. This environmental DNA is taken up by competent bacteria (i.e., bacteria able to take up extracellular DNA) and is recombined into the bacterial genome or remains separate as a plasmid.
Transduction: Small sequences of chromosomal DNA are moved from one bacterium to another via a bacteriophage.
Conjugation: DNA is transferred from one bacterial cell to another through direct contact using a conjugation pilus.
Card 243
Ames Test
Key Points/Steps
Answer
Ames Test
Screening test used to determine whether a specific chemical can cause mutations in bacteria. If a chemical is mutagenic, it may also be carcinogenic (i.e., cancer-causing).
Uses an auxotrophic strain of Salmonella that cannot synthesize the amino acid histidine, along with rat liver extract.
Two agar plates are prepared without histidine. Bacteria exposed to the chemical are placed on the experimental plate, and bacteria not exposed to the chemical are placed on the control plate.
If the chemical is mutagenic, it will cause some bacteria to grow in the absence of histidine on the experimental plate (i.e., gain the ability to synthesize their own histidine).
The number of colonies on the experimental plate, as compared to the control plate, indicates the degree to which the substance is mutagenic.
Card 244
Replica Plating
Key Points/Steps
Answer
Replica Plating
Technique used to identify auxotrophs (i.e., bacteria that are unable to synthesize a required nutrient due to a genetic mutation).
Bacterial cells are removed from a master plate using sterile velvet and pressed onto a nutritionally complete plate and a nutritionally incomplete plate. Colonies are placed in the exact same position on the two plates for easy comparison after incubation.
Auxotrophic mutants are unable to grow on the nutritionally incomplete medium. The colonies that failed to grow on the nutritionally incomplete plate can be recovered from the nutritionally complete plate for further research.
Card 245
DNA Repair
Proofreading
Mismatch Repair
Repair of Thymine Dimers
Answer
DNA Repair
Proofreading: DNA polymerase checks for accuracy during DNA replication and excises any incorrect bases and replaces them with the correct bases before resuming DNA replication.
Mismatch Repair: Correction of errors after replication. Enzymes recognize the mismatched base, excise it, and replace it with the correct one.
Repair of Thymine Dimers:
- Nucleotide Excision Repair (Dark Repair): Enzymes cut the DNA upstream and downstream of the thymine dimer and remove the damaged section. DNA polymerase replaces the missing nucleotides and ligase seals the strand where the cuts were made.
- Direct Repair (Light Repair): Occurs through the process of photoreactivation. In the presence of visible light, the enzyme photolyase breaks the bond between thymine bases, allowing thymines to correctly base pair with adenines on the complementary strand.
Card 246
Mutagens
Chemical Mutagens
Radiation
Answer
Mutagens
Chemical or physical agents capable of inducing changes in the DNA.
Chemical Mutagens:
- Nucleoside Analogs: Chemicals that are structurally similar to normal nucleotide bases that are incorporated into DNA during replication (e.g., acyclovir).
- Nucleotide-Modifying Agents: Chemicals that modify normal DNA bases (e.g., nitrous acid).
- Intercalating Agents: Chemicals that cause atypical spacing between base pairs, leading to frameshift mutations (e.g., ethidium bromide).
Radiation:
- Ionizing Radiation: Causes single and double stranded breaks in DNA by forming hydroxyl radicals (e.g., X-rays, gamma rays).
- Nonionizing Radiation: Creates thymine dimers, which may cause DNA replication errors or frameshift/point mutations (e.g., UV light).
Mutations
Change in the DNA sequence of an organism. Spontaneous mutations are caused by errors in DNA replication. Induced mutations are caused by exposure to a chemical mutagen or radiation.
Point Mutation: A mutation that affects a single nucleotide, most commonly resulting in a base substitution.
- Silent Mutation: Does not alter the amino acid sequence, due to degeneracy of the genetic code.
- Missense Mutation: Causes a different amino acid to be incorporated into the polypeptide.
- Nonsense Mutation: Replaces a codon for an amino acid with a stop codon.
NONsense mutations lead to NONfunctional proteins!
Insertion/Deletion: A mutation that results from either the addition of one or more bases (insertion) or the removal of one or more bases (deletion).
- Frameshift Mutation: Causes a shift in the reading frame (i.e., how codons are read during translation), altering every amino acid after the point of mutation.
Card 249
Translation
Illustration
Answer
Translation
Card 250
Translation
Elongation
Termination
Answer
Translation
Elongation:
- The tRNA carrying the second amino acid pairs with the next codon on the mRNA at the A site.
- The first and second amino acids are joined by a peptide bond by the ribosome. Methionine is released from the initiator tRNA (in the P site) and remains bound to the amino acid of the second tRNA (in the A site).
- The ribosome moves forward by one codon (i.e., translocation). The initiator tRNA shifts to the E site and detaches. The second tRNA moves to the P site, leaving a new codon exposed at the A site.
- The ribosome continues to move forward in this fashion, adding new amino acids to the growing polypeptide.
Termination: When the ribosome reaches a stop codon (i.e., UAA, UAG, or UGA) at the A site, the polypeptide is released and the large and small ribosomal subunits separate.
Card 251
Translation
Initiation
Answer
Translation
Decoding of mRNA to create a polypeptide (i.e., chain of amino acids).
Initiation:
- The large ribosomal subunit, small ribosomal subunit, mRNA, and the initiator tRNA carrying the first amino acid (methionine) come together to form the initiation complex.
- The small ribosomal subunit scans the mRNA for a start codon (AUG) and binds to the mRNA.
- The UAC anticodon on the initiator tRNA pairs with the complementary AUG codon on the mRNA.
- The large ribosomal subunit clamps down on the mRNA, initiator tRNA, and small ribosomal subunit, securing the tRNA at the P site.
Genetic Code
A set of instructions that direct the translation of mRNA into amino acids.
Codons: Groups of 3 nucleotides that correspond to an amino acid. 64 possible combinations.
Start Codon: AUG codon. Initiates translation and codes for the amino acid methionine.
Degeneracy: Redundancy in the genetic code, as there are 64 possible codons, but only 20 amino acids (i.e., multiple codons code for the same amino acid).
Wobble Position: The third position in a codon that, if altered, often produces the same amino acid as the unaltered codon.
Nonsense (Stop) Codon: Does not code for an amino acid. Stops protein synthesis and releases the polypeptide.
Card 254
Transcription in Eukaryotes
Primary Transcript
5' Cap
Poly-A Tail
Exons
Introns
RNA Splicing
Answer
Transcription in Eukaryotes
Primary Transcript: RNA sequence synthesized by RNA polymerase in the nucleus, undergoes several processing steps.
5' Cap: Inverted guanine nucleotide added to the 5' end of the primary transcript in the nucleus. Prevents degradation and helps the ribosome bind to the mRNA.
Poly-A Tail: Multiple adenine nucleotides (50 - 200+) added to the 3' end of the transcript, slowing degradation. It also signals that the transcript needs to be exported to the cytoplasm.
Exons: Sequences in eukaryotic genes that encode for amino acids.
Introns: Sequences in eukaryotic genes that do not encode for amino acids.
RNA Splicing: Introns are removed from the primary transcript by a spliceosome.
Exons are Expressed and NOT Excised.
Alternative splicing allows exons to be joined in different combinations, resulting in different mRNA transcripts to be generated from the same gene.
Card 255
Transcription
Illustration
Answer
Transcription
Card 256
Transcription
Initiation
Elongation
Termination
Answer
Transcription
Process of synthesizing mRNA (i.e., messenger RNA) using the information encoded in DNA.
Initiation: RNA polymerase binds to the DNA at the promoter site.
Elongation: Moving along (i.e., reading) the DNA template, RNA polymerase synthesizes a complementary daughter RNA strand in the 5' to 3' direction.
- "G" in DNA → "C" in RNA
- "C" in DNA → "G" in RNA
- "T" in DNA → "A" in RNA
- "A" in DNA → "U" in RNA
The RNA transcript includes a "U" instead of a "T" nucleotide.
Termination: Transcription stops once RNA polymerase reaches the terminator site on the DNA template strand, releasing the RNA molecule.
Card 257
DNA Replication
Key Differences in Eukaryotes vs. Prokaryotes
Answer
DNA Replication
Eukaryotes
Prokaryotes
Multiple linear chromosomes.
One circular chromosome.
Multiple origins of replication per chromosome.
1 Origin of replication per chromosome.
Chromosomes contain telomeres
(i.e., regions of non-coding repetitive sequences at the end of chromosomes that protect coding sequences from being lost during cell division).
Chromosomes do not contain telomeres.
Card 258
DNA Replication: Semiconservative Replication
Illustration
Answer
DNA Replication: Semiconservative Replication
Card 259
DNA Replication in Prokaryotes
Elongation
Termination
Answer
DNA Replication in Prokaryotes
Elongation:
- DNA polymerase III extends the RNA primers, adding DNA nucleotides in the 5' to 3' direction only!
- The leading strand only requires one RNA primer and is synthesized continuously.
- The lagging strand is synthesized discontinuously in short Okazaki fragments, each of which must start with its own RNA primer.
- As synthesis proceeds, RNA primers are replaced with DNA by DNA polymerase I.
- Nicks in the DNA (from the replacement of primers) are sealed by DNA ligase.
Termination:
- DNA polymerase III halts when replication forks meet.
- Two circular genomes are separated by topoisomerase IV.
Card 260
DNA Replication in Prokaryotes
Semiconservative Replication
Initiation of Replication
Answer
DNA Replication in Prokaryotes
Semiconservative Replication: Two strands of the double helix separate during DNA replication, each strand serves as a template from which the new strand is copied. After replication, each new double-stranded DNA includes one parental DNA strand and one new daughter DNA strand.
Initiation of Replication:
- Occurs at the origin of replication.
- Gyrase relaxes the supercoiled DNA.
- Helicase unwinds and separates the DNA helix into single-stranded DNA (i.e., breaks the hydrogen bonds between the strands).
- Proteins stabilize the unwound single-stranded DNA.
- As the DNA opens up, two replication forks are formed, creating a "replication bubble".
- DNA Primase synthesizes short RNA primers, which are complementary to the parenteral DNA strand.
Genes & Gene Expression
Gene: Segment of DNA coding for the production of a specific polypeptide (i.e., basic component of a protein).
Genotype: Organism's full collection of genes.
Gene Expression: Synthesis of a protein through the process of transcription and translation.
Phenotype: Observable characteristics that result from the expression of genes under specific environmental conditions.
Genotype = Genetic make-up and Phenotype = Physical characteristic.
Central Dogma of Molecular Biology:
Card 262
DNA Structure
Illustration
Answer
DNA Structure
Card 263
DNA Structure
Sugar-Phosphate Backbone
Double Helix
Base Pairing
Answer
DNA Structure
Sugar-Phosphate Backbone: Phosphodiester bonds form between the 3' hydroxyl group of one nucleotide to the 5' phosphate group of the next nucleotide. This forms a nucleic acid strand with alternating phosphate and sugar molecules.
New nucleotides are always added to the 3' end of the molecule!
Double Helix: The two DNA strands are antiparallel (i.e., one strand runs in the 5' to 3' direction, while the other strand runs in the 3' to 5' direction). The two strands of DNA wind around each other to form a helix, which resembles a twisted ladder.
Base Pairing: Hydrogen bonding of specific purines to specific pyrimidines on the two antiparallel strands of DNA form the "rungs" of the ladder.
Complementary base pairs include A-T and C-G between the 2 strands.
Card 264
Nucleotides
Deoxyribose/Ribose
Phosphate Group
Nitrogenous Bases
Answer
Nucleotides
Building blocks of nucleic acids. Composed of a 5-carbon sugar (i.e., deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base.
Deoxyribose/Ribose: 5-Carbon sugar molecule. Carbon atoms are numbered 1', 2', 3', 4', and 5' (1' is read as "one prime").
- 1' Carbon: Carbon connected to the nitrogenous base.
- 3' Carbon: Carbon connected to the hydroxyl group. Used to attach to the next nucleotide in the chain.
- 5' Carbon: Carbon connected to the phosphate group. Used to attach to the previous nucleotide in the chain.
Phosphate Group: Phosphorus atom bonded to 4 oxygen atoms. Carries a negative charge.
Nitrogenous Bases: Nitrogen-containing ring structure, responsible for base pairing between nucleic acid strands.
- Purines: Adenine (A), guanine (G).
- Pyrimidines: Cytosine (C), thymine (T). Uracil (U) replaces thymine in RNA.
Biogeochemical Cycles
Sulfur Cycle:
- Sulfur is found in the atmosphere as SO2 and is dissolved in precipitation. It is also released by rocks via weathering and combines with oxygen in the air to form sulfate (SO42-).
- Plants take in sulfur, and plants are consumed by animals. During decomposition of dead plants/animals, microbes remove sulfur groups from amino acids. This produces hydrogen sulfide (H2S) gas, which is released back into the atmosphere.
Phosphorus Cycle:
- Most phosphorus is found in rocks and sediments. Weathering causes rocks to release phosphate ions (PO43-) into the water and soil.
- Plants take in inorganic phosphate, and plants are consumed by animals. Organic phosphate is released into the soil when plants/animals die, and bacteria convert organic phosphorus back to its inorganic form.
Biogeochemical Cycles: Nitrogen Cycle
Recycling of nitrogen between organisms and the environment.
Nitrogen Fixation: Conversion of atmospheric nitrogen gas (N2) to ammonia (NH3). by free-living and symbiotic prokaryotes under anaerobic conditions.
Nitrification: Conversion of ammonia (NH3) to nitrite (NO2) and then to nitrate (NO3) by nitrifying prokaryotes under aerobic conditions.
Assimiliation: Inorganic nitrogen compounds from the environment are taken up by plants and other organisms and converted to organic nitrogen compounds (e.g., amino acids).
Ammonification: Conversion of organic nitrogen compounds found in nitrogenous waste from living organisms or in the remains of dead organisms into ammonia by decomposers (i.e., prokaryotes, fungi).
Denitrification: Conversion of nitrate (NO3) to atmospheric nitrogen gas (N2) by denitrifying bacteria under anaerobic conditions.
Biogeochemical Cycles: Carbon Cycle
Recycling of carbon between organisms and the environment.
Fixation: Photoautotrophs (e.g., cyanobacteria, plants, algae) convert CO2 into organic molecules during photosynthesis.
Decomposition: Chemoheterotrophs (e.g., animals) break down organic molecules during cellular respiration, producing CO2. Microbes in the soil and water oxidize organic compounds in dead plants and animals, producing CO2 or methane (CH4).
Storage: Carbon can be found in rocks (e.g., limestone) and in the ocean as the bicarbonate ions. Burning of fossil fuels releases CO2 into the atmosphere, leading to planetary heat retention.
Card 269
Chemical Requirements
Carbon
Nitrogen
Phosphorus
Sulfur
Trace Elements
Answer
Chemical Requirements
Carbon: Basic building block of life. Primary component of all macromolecules (e.g., carbohydrates, proteins, lipids, nucleic acids).
Nitrogen: Needed for the synthesis of amino acids, nucleic acids (i.e., RNA, DNA), and adenosine triphosphate (ATP). Major component of chlorophyll, a pigment needed for photosynthesis.
Phosphorus: Needed for the synthesis of nucleic acids, ATP, and phospholipids (e.g., plasma membrane).
Sulfur: Required for the synthesis of amino acids (e.g., cysteine and methionine), disulfide bonds in polypeptide chains, and enzymes (e.g., coenzyme A).
Trace Elements: Used as enzyme co-factors (e.g., iron, copper, zinc).
Card 270
Culture Media
Chemically Defined Media
Complex Media
Selective Media
Differential Media
Enrichment Media
Answer
Culture Media
Liquid, solid, or semi-solid substances designed to support the growth of microorganisms in a laboratory.
Chemically Defined Media: The complete chemical composition of the medium is known.
Complex Media: Contains extracts and digests of yeast, plants, or meats. Precise chemical composition is unknown, varies from batch to batch.
Selective Media: Supports the growth of the wanted microorganisms and inhibits the growth of the unwanted microorganisms.
Differential Media: Allows different microorganisms to be visually distinguished based on a change in the color of the colonies or medium.
Enrichment Media: Provides conditions that enhance the growth of fastidious microorganisms (i.e., microorganisms that are very particular about their nutrients and/or environment) and microorganisms present in low numbers.
pH & Osmotic Requirements
Neutrophiles: Organisms that grow best at a neutral pH (~ 6.5 - 7.5).
Acidophiles: Organisms that grow best in an acidic environment (i.e., pH
Alkaliphiles: Organisms that grow best in an alkaline environment (i.e., pH > 9.0).
Halophiles: Organisms that require high salt concentrations for growth.
Halotolerant: Do not require high salt concentrations for growth, but can grow in the presence of high salt.
Protein stability is affected by variations in pH.
Card 272
Temperature Requirements
Mesophiles
Psychrotrophs
Psychrophiles
Thermophiles
Hyperthermophiles
Answer
Temperature Requirements
Mesophiles: Organisms adapted to moderate temperatures (~ 20°C - 45°C). The majority of human pathogens are mesophilic.
Psychrotrophs: Organisms that prefer cooler temperatures (~ 4°C - 25°C). Responsible for spoilage of refrigerated foods.
Psychrophiles: Cold loving organisms. Optimal growth temperature ≈ 15°C, but can grow in temperatures under 0°C.
"Psychro-" = "Cold". I hate the cold, it makes me psycho!
Thermophiles: Heat loving organisms (~ 50°C - 80°C).
Hyperthermophiles: Organisms that grow in extreme heat (~ 80°C - 110°C).
Protein stability and membrane fluidity is affected by temperature changes.
Oxygen & Carbon Dioxide Requirements
Obligate Aerobes: Organisms that require oxygen to survive.
Obligate Anaerobes: Organisms that cannot survive in the presence of oxygen.
Facultative Anaerobes: Organisms that grow best with oxygen, but can survive without it.
Aerotolerant Anaerobes: Organisms that do not use oxygen for growth, but are not harmed by its presence.
Microaerophiles: Organisms that require low levels of oxygen for growth. Many microaerophiles are also capnophiles.
Capnophiles: Organisms that require an increased CO2 concentration.
Card 275
Quorum Sensing
Key Characteristics
Answer
Quorum Sensing
A means of bacterial communication that allows bacteria to "turn on" group behaviors once the population reaches a threshold density.
Key Characteristics:
- Bacteria release small, diffusible molecules called autoinducers.
- When the bacterial population reaches a critical threshold (called a quorum), the autoinducers bind to receptors in the cytoplasm or on the surface of the bacterial cells.
- The autoinducer/receptor complex binds to DNA promoters and activates gene transcription.
- This process allows bacteria to synthesize virulence factors only when the population is sizable enough to overwhelm the immune defenses of the host.
Card 276
Biofilms
Biofilm Formation
Key Characteristics
Answer
Biofilms
Aggregation of microbes enclosed in an extracellular polymeric substance (EPS) matrix, forming a slimy layer on a surface.
Biofilm Formation: Planktonic cells (free-floating microbes) attach to a surface, becoming sessile (unable to move freely). Microbes produce EPS and water channels, which allow for the transport of nutrients and wastes within the biofilm.
Sessile is cessation of movement.
Key Characteristics:
- Optimal environment for the exchange of genetic material between cells.
- Allows for quorum sensing (i.e., cell to cell communication).
- Allows for metabolic collaboration, such that the waste product of one organism becomes the nutrient for another.
- Provides shelter from environmental hazards (e.g., antibiotics).
Biofilms play a significant role in infectious disease and medical device-related infections.
Card 277
Indirect Measurement of Bacterial Growth
Turbidity
Dry Weight
Metabolic Activity
Answer
Indirect Measurement of Bacterial Growth
Turbidity: Measurement of the cloudiness of a sample using a spectrophotometer. ↑ Numbers of bacteria cause ↑ turbidity and ↓ light to reach the detector.
Dry Weight: Measurement of the dry weight of a culture sample. Sample must be concentrated, washed, and dried prior to weighing. Useful for filamentous (e.g., thread-like) microorganisms.
Metabolic Activity: Measurement of cell activity by monitoring metabolic products or disappearance of reactants (e.g., oxygen consumption, ATP formation).
Card 278
Most Probable Number (MPN)
Illustration:
- MPN Presumptive Test for Fecal Coliforms
Answer
Most Probable Number (MPN)
Card 279
Direct Measurement of Bacterial Growth
Most Probable Number (MPN) Method
Answer
Direct Measurement of Bacterial Growth
Statistical method for estimating the number of viable microorganisms in a dilute sample. Evaluates detectable growth by observing changes in turbidity or color due to metabolic activity.
- First set of 5 nutrient broth tubes are inoculated with 10 mL of the sample.
- Second set of 5 nutrient broth tubes are inoculated with 1 mL of the sample.
- Third set of 5 nutrient broth tubes are inoculated with 0.1 mL of the sample.
- After incubation, tubes are examined for microbial growth or other characteristics based on the specific test being performed.
- Number of positive tubes in each of the 3 sets (e.g., 5, 2, 0) is used to determine the most probable number of bacteria from an MPN table.
MPN is often used to determine the extent of fecal contamination by coliform bacteria (i.e., bacteria found in the intestinal tract of animals).
Card 280
Direct Measurement of Bacterial Growth
Membrane Filtration Technique
Answer
Direct Measurement of Bacterial Growth
Method used to estimate bacterial growth in very dilute fluid samples (e.g., drinking water).
- Known volume of liquid is vacuum filtered through a membrane.
- Membrane is transferred to a petri plate containing a medium.
- Plate is incubated and colonies are counted.
- Divide the number of colonies by the volume of the filtered liquid. Results are reported in colony-forming units per mL.
Card 281
Serial Dilution
Illustration
Answer
Serial Dilution
Number of cells in original concentration = # colonies x dilution factor x volume sample inoculated to plate.
47 x 10,000 x 1.0 = 470,000 CFU/mL
Card 282
Direct Measurement of Bacterial Growth
Direct Cell Count
Plate Count
Serial Dilution
Answer
Direct Measurement of Bacterial Growth
Direct Cell Count: Direct estimate of how many organisms are present in a sample by counting cells in a liquid culture. Uses a calibrated slide (e.g., Petroff-Hausser chamber) or electronic cell-counting device (e.g., Coulter counter). Counts both viable and nonviable cells.
Plate Count: A count of viable or live cells, usually expressed as colony-forming units per mL (CFU/mL). Pour plate and spread plate methods are used to inoculate plates before performing a plate count.
Serial Dilution: Process of diluting a liquid sample several times to obtain a plate with 30 - 300 CFU/mL (i.e., a countable number). First step before pour or spread plate method.
Card 283
Plating Methods
Pour Plate Method
Spread Plate Method
Answer
Plating Methods
Techniques used in the laboratory to isolate, count, and grow microorganisms.
Pour Plate Method: Bacterial sample is mixed with liquid agar. Sample is poured onto a sterile petri dish, swirled to mix, and allowed to solidify. Plate is incubated to allow for colony growth. Suitable for aerobic and facultative anaerobic bacteria.
Colonies may form on and beneath the agar surface.
Spread Plate Method: Bacterial sample is pipetted onto solid agar and spread evenly using a sterile spreader. Sample is incubated to allow for colony growth. Suitable for aerobic or facultative aerobic bacteria only.
Colonies form on the agar surface.
Card 284
Bacterial Growth Curve
Illustration
Answer
Bacterial Growth Curve
Card 285
Bacterial Growth
Generation Time
Bacterial Growth Phases
Answer
Bacterial Growth
Generation Time (Doubling Time): Time required for a cell to divide or a population to double.
Bacterial Growth Phases:
- Lag Phase: No increase in the number of living bacterial cells. Characterized by ↑ metabolism and protein synthesis.
- Log Phase: Exponential increase in the number of living bacterial cells. Characterized by constant growth rate and metabolism. # New cells > # Dying cells.
- Stationary Phase: Growth rate stalls due to accumulation of waste products and depletion of nutrients. # New cells = # Dying cells.
- Death Phase: Exponential decrease in the number of living bacterial cells. # New cells
Lag phase comes before log phase because 'a' comes before 'o' in the alphabet!
Card 286
Binary Fission
Illustration
Answer
Binary Fission
Card 287
Binary Fission
Steps in Binary Fission
Answer
Binary Fission
One cell divides into two daughter cells, with each offspring receiving a complete copy of the parental genome. Most common mechanism for cell replication in bacteria.
Steps in Binary Fission:
- DNA is replicated, starting at the origin of replication.
- Cell elongates, and the two DNA molecules migrate to opposite sides of the cell.
- Septum forms in the middle of the cell.
- Cells separate, with each daughter cell receiving a complete copy of the parental genome.
Binary fission is a form of asexual reproduction.
Photosynthesis
Oxygenic Photosynthesis:
- O2 is generated as a byproduct.
- Chemical reaction: 6CO2 + 6H2O → C6H12O6 + 6O2.
- Uses H2O as the electron donor.
- Examples: Cyanobacteria, algae, and plants.
Oxygenic photosynthesis is the opposite of aerobic respiration!
Anoxygenic Photosynthesis:
- O2 is not generated as a byproduct.
- Uses a molecule other than H2O as the electron donor (e.g., H2S).
- Examples: Green and purple sulfur bacteria.
Photosynthesis
Process used by phototrophic organisms to convert sunlight into chemical energy, driving the production of sugars.
Light-Dependent Reactions: Energy from the sun is absorbed by photosynthetic pigments (e.g., chlorophylls) and converted into stored chemical energy (i.e., ATP and NADPH), a process referred to as photophosphorylation. During oxygenic photosynthesis, electrons are removed from water, and the splitting of water molecules releases oxygen gas.
Photophosphorylation is like oxidative phosphorylation except the energy source is different (sunlight vs. chemical energy)!
Light-Independent Reactions (Calvin Cycle): Chemical energy from light-dependent reactions is used to fix CO2 (i.e., conversion of carbon dioxide into a sugar molecule).
Card 290
Lipid & Protein Catabolism
Lipid Catabolism
Protein Catabolism
Answer
Lipid & Protein Catabolism
Lipid Catabolism:
- Lipase removes fatty acid chains from the glycerol backbone.
- Glycerol is converted to glyceraldehyde 3-phosphate and continues through glycolysis.
- Fatty acids are catabolized through β-oxidation. Two-carbon acetyl groups are removed from the fatty acid chain and enter the Krebs cycle.
Protein Catabolism:
- Extracellular proteases break proteins down into smaller peptides, which are taken up by cells.
- Intracellular proteases break down peptides into individual amino acids.
- Amino group is removed by enzymes (i.e., deamination), and the remaining molecule can enter the transition reaction or Krebs cycle.
Card 291
Types of Metabolism: Comparison
Aerobic Respiration
Anaerobic Respiration
Fermentation
Answer
Types of Metabolism: Comparison
Type of Metabolism
Processes Involved
Final Electron Acceptor
Maximum Yield of ATP
Aerobic Respiration
Glycolysis
Transition Phase
Citric Acid (Krebs) Cycle
Oxidative Phosphorylation
Oxygen
38 ATP
Anaerobic Respiration
Glycolysis
Transition Phase
Citric Acid (Krebs) Cycle Oxidative Phosphorylation
Nitrate, sulfate, carbonate, others
Variable
(
Fermentation
Glycolysis
Fermentation
Organic molecule
(e.g., pyruvate)
2 ATP
Fermentation
Anaerobic process that releases energy from organic molecules (e.g., glucose), producing a small amount of ATP. Begins with glycolysis but does not include the citric acid cycle or electron transport chain.
Lactic Acid Fermentation: Pyruvate from glycolysis is reduced by NADH to form lactic acid. NADH is oxidized to NAD⁺. Used in the production of yogurt and by muscle cells during oxygen depletion.
- Types of Microorganisms: Bacteria (e.g., Lactobacillus), fungi.
Alcohol Fermentation: Pyruvate from glycolysis is converted into acetaldehyde and CO₂. Acetaldehyde is then reduced by NADH to make ethanol. NADH is oxidized to NAD⁺. Used to make alcoholic beverages, bread, and biofuels.
- Types of Microorganisms: Yeast (e.g., Saccharomyces cerevisiae), bacteria.
Fermentation and anaerobic respiration are NOT the same!
Card 293
Oxidative Phosphorylation
Illustration
Answer
Oxidative Phosphorylation
Card 294
Oxidative Phosphorylation
Electron Transport Chain (ETC)
Chemiosmosis
Answer
Oxidative Phosphorylation
Electron Transport Chain (ETC):
- High energy electrons from NADH and FADH2 are passed from one ETC carrier complex to the next in a series of redox reactions, releasing energy that forms a proton gradient.
- Final electron acceptor is oxygen with aerobic respiration, and a substance other than oxygen in anaerobic respiration.
Chemiosmosis:
- Energy from the proton gradient is used to drive production of ATP.
- In prokaryotes, hydrogen ions flow from the extracellular space into the cytoplasm (i.e., down the electrochemical gradient) through ATP synthase, a protein complex in the membrane.
- In eukaryotes, movement is from the intermembrane space of the mitochondrion into the matrix.
Card 295
Oxidative Phosphorylation
Input
Steps
Net Output
Answer
Oxidative Phosphorylation
Generation of ATP using the chemical energy in carbohydrates. Occurs along the inner mitochondrial membrane for eukaryotes and along the plasma membrane for prokaryotes.
Input: 10 NADH, 2 FADH2, final electron acceptor (e.g., 6O2 in aerobic respiration).
Steps:
- Electron Transport Chain.
- Chemiosmosis.
Net Output: 10 NAD+, 2 FAD molecules.
- Aerobic Metabolism: Up to 34 ATP in prokaryotes (less in eukaryotes), 6 water (H2O).
- Anaerobic Metabolism: ATP varies (less than aerobic metabolism), final products will vary.
Card 296
Citric Acid (Krebs) Cycle
Illustration
Answer
Citric Acid (Krebs) Cycle
Card 297
Citric Acid (Krebs) Cycle
Input
Steps
Net Output
Answer
Citric Acid (Krebs) Cycle
Sequence of biochemical reactions used to generate energy. Occurs in the cytoplasm for prokaryotes and in the mitochondria in eukaryotes. Also known as the tricarboxylic acid (TCA) cycle.
Input: 2 acetyl-CoA, 3 NAD+, 2 FAD molecules.
Steps:
- Acetyl group from acetyl-CoA is attached to a 4-carbon oxaloacetate molecule to form a 6-carbon citrate molecule.
- Citrate is oxidized in a series of steps, releasing 1 ATP, 3 NADH, 1 FADH2, and 2 CO2.
Two turns of the Krebs cycle is required to process all the carbon from one glucose molecule.
Net Output: 2 ATP, 6 NADH, 2 FADH2, 4 CO2 molecules.
Card 298
Transition (Bridge) Reaction
Input
Steps
Net Output
Answer
Transition (Bridge) Reaction
Preparatory step that takes place before pyruvate (produced in glycolysis) can enter the citric acid cycle. Occurs in the cytoplasm for prokaryotes and in the mitochondrial matrix in eukaryotes.
Input: 2 Pyruvate, 2 NAD+ molecules.
Steps:
- Carboxyl group is removed from each pyruvate molecule, releasing CO2.
- The remaining 2-carbon acetyl group is attached to coenzyme A (CoA), forming acetyl-CoA.
- NAD+ is reduced to NADH.
Net Output: 2 acetyl-CoA, 2 NADH, 2 CO2 molecules.
No ATP is generated in the transition reaction!
Card 299
Glycolysis
Illustration
Answer
Glycolysis
Card 300
Glycolysis
Input
Steps
Net Output
Answer
Glycolysis
Most common pathway for catabolism of glucose. Occurs in the cytoplasm and is anaerobic (i.e., does not require oxygen). Also called the Embden-Meyerhof-Parnas (EMP) pathway.
Input: 1 glucose, 2 NAD+ molecules.
Steps:
- Energy Investment Phase: Glucose is split into two 3-carbon molecules called glyceraldehyde 3-phosphate (G3P) using the energy from 2 ATP.
- Energy Payoff Phase: G3P is oxidized to pyruvate, producing 4 ATP. 2 NAD+ are reduced to 2 NADH.
Net Output: 2 Pyruvate, 2 ATP, and 2 NADH molecules.
Cellular Respiration
Aerobic Respiration: Type of respiration used by aerobes (i.e., organisms that use oxygen).
- Includes: glycolysis, transition reaction, citric acid (Krebs) cycle, and oxidative phosphorylation (electron transport chain and chemiosmosis).
- Final electron acceptor is oxygen.
- Chemical reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O.
Anaerobic Respiration: Type of respiration used by anaerobes (i.e., organisms that do not require oxygen).
- Includes the same steps as aerobic respiration, but the final electron acceptor is a substance other than oxygen (e.g., sulfate, nitrate).
- Less ATP is generated as the electron acceptors have a lower reduction potential vs. oxygen.
Some sources consider glycolysis followed by fermentation under anoxic conditions as anaerobic respiration.
Card 302
Carbon and Energy Source
Phototroph
Chemotroph
Autotroph
Heterotroph
Answer
Carbon and Energy Source
Phototroph: Organism that obtains energy from the sunlight to carry out metabolic processes.
Chemotroph: Organism that obtains energy from the breakdown of chemical compounds to carry out metabolic processes.
Autotroph: Organism that obtains carbon from carbon dioxide (i.e., converts inorganic carbon dioxide into organic sugar molecules).
Heterotroph: Organism that cannot make its own food and obtains carbon from other organisms.
Autotrophs can make their own food, whereas heterotrophs have to mooch off of others!
Plants are photoautotrophs, converting sunlight, CO2, and water into sugars during the process of photosynthesis. Animals are chemoheterotrophs, breaking down organic molecules during respiration for energy.
Enzyme-Substrate Binding
Competitive Inhibitor: Molecule similar to the substrate that binds to the enzyme's active site, blocking the substrate from binding. Lowers enzyme activity.
Noncompetitive (Allosteric) Inhibitor: Binds to the enzyme at an allosteric site (i.e., location away from the active site). Causes a conformational change that alters the shape of the active site, preventing enzyme activity.
Allosteric Activator: Binds to the enzyme at an allosteric site, causing a conformational change that increases enzyme activity.
Feedback Inhibition: When there is excess end product available, the end product acts as an allosteric inhibitor, which decreases enzyme activity. Also called "negative feedback".
Card 305
Enzymes
Illustration
Answer
Enzymes
Card 306
Enzymes
Substrate
Active Site
Apoenzyme
Cofactor/Coenzyme
Holoenzyme
Answer
Enzymes
Substrate: Substance that reacts with an enzyme in a chemical reaction.
Active Site: Location on the enzyme where the substrate binds.
Apoenzyme: Inactive protein portion of an enzyme, requires a cofactor and/or coenzyme for activation.
Cofactor/Coenzyme: "Helper" molecules required for an enzyme to be activated.
- Cofactor: Inorganic ion (e.g., Fe2+, Mg2+).
- Coenzyme: Organic molecule (e.g., ATP, NADH, vitamins).
Holoenzyme: Whole, active enzyme (i.e., apoenzyme + necessary cofactor/coenzyme).
Card 307
Enzymes
Factors Affecting Enzyme Activity
Answer
Enzymes
Catalysts for biochemical reactions in a cell. Lower the activation energy required for chemical reactions to occur. Not used up in the reactions (i.e., reusable).
Factors Affecting Enzyme Activity:
- pH: Enzymes function best within an optimal pH range. Extreme pH (i.e., acidic or basic) can denature enzymes (i.e., alter the three dimensional structure of enzymes).
- Temperature: ↑ Temperature generally increases chemical reaction rates. Temperatures outside the optimal temperature range can ↓ enzyme activity.
- Substrate Concentration: ↑ Substrate concentration = ↑ enzyme activity until the saturation point is reached (i.e., all active sites are occupied).
Card 308
Energy Carriers
Electron Carriers
Adenosine Triphosphate (ATP)
Answer
Energy Carriers
Electron Carriers: Molecules that bind high-energy electrons and shuttle them to components of the electron transport chain. Important electron carriers:
- Nicotinamide Adenine Dinucleotide (NAD+/NADH).
- Nicotinamide Adenine Dinucleotide Phosphate (NADP+/NADPH).
- Flavin Adenine Dinucleotide (FAD/FADH2).
Adenosine Triphosphate (ATP): "Energy currency" of the cell. Stores chemical energy in its high-energy phosphate bonds for later use to drive processes that require energy.
Oxidation-Reduction Reactions
Oxidation Reactions: Reactions that remove high-energy electrons from donor molecules during the breaking of chemical bonds, leaving them oxidized.
Reduction Reactions: Reactions that add high-energy electrons to acceptor molecules, leaving them reduced.
Redox Reactions: Pairing of an oxidation and reduction reaction. Important in the conversion of chemical energy found in organic molecules into the chemical energy found in the bonds of ATP. These reactions always occur together!
OIL RIG: Oxidation Is Loss, Reduction Is Gain of high-energy electrons.
Metabolism
All chemical reactions inside a cell.
Endergonic: Reactions that require energy to proceed.
Exergonic: Spontaneous reactions that release energy.
Catabolism: Exergonic pathways that break down complex molecules into simpler ones (i.e., decomposition reactions). Molecular energy stored in the complex bonds is released, which is then used to drive anabolism.
Anabolism: Endergonic metabolic pathways involving the conversion of simple molecular building blocks into more complex molecules, fueled by cellular energy (i.e., synthesis reactions).
Card 311
Chemical Reactions
Reactants
Arrow
Products
Types of Reactions
Answer
Chemical Reactions
The process of either forming or breaking bonds between atoms.
Reactants: The starting substance(s) in a chemical reaction.
Arrow: Separates the reactants from the products and shows the direction in which the reaction proceeds.
Products: The substance(s) formed from the reaction.
Types of Reactions:
- Synthesis Reaction: A + B → AB
- Decomposition Reaction: AB → A + B
- Single Replacement: AB + C → B + AC
- Double Replacement: AB + CD → AD + BC
- Reversible Reaction: A + B ⇌ AB
Card 312
Membrane Transport: Eukaryote Specific Mechanisms
Endocytosis
Exocytosis
Answer
Membrane Transport: Eukaryote Specific Mechanisms
Endocytosis: Uptake of matter through the plasma membrane.
- Phagocytosis: Uptake of large particles. Cell membrane surrounds the particle and pinches off to form an intracellular vacuole.
- Pinocytosis: Uptake of small, dissolved materials and liquids. Cell membrane surrounds a small amount of fluid and pinches off to form an intracellular vesicle.
- Receptor-Mediated Endocytosis: Endocytosis is triggered when specific molecules bind to receptors on the cell surface.
Pinocytosis is like sipping a pinot wine (i.e., liquid).
Exocytosis: Process in which and intracellular vesicle fuses with the cell membrane and ejects the contents of the vesicle out of the cell.
Card 313
Membrane Transport: Osmosis
Illustration:
- Effect of Osmotic Pressure on Cells with a Cell Wall
Answer
Membrane Transport: Osmosis
Card 314
Membrane Transport: Osmosis
Illustration:
Effect of Osmotic Pressure on Cells without a Cell Wall
Answer
Membrane Transport: Osmosis
Card 315
Membrane Transport: Osmosis
Cell Changes with a Hypertonic Solution
Cell Changes with a Hypotonic Solution
Answer
Membrane Transport: Osmosis
Hypertonic Solution:
- In cells with a cell wall, plasmolysis occurs (i.e., plasma membrane shrinks and detaches from the cell wall).
- In cells without a cell wall, crenation occurs (i.e., shriveling of the cell) due to dehydration.
Hypotonic Solution:
- In cells with a cell wall, there is increased protection against lysis (i.e., bursting of the cell).
- In cells without a cell wall, the cell expands and eventually lyses.
Card 316
Membrane Transport: Osmosis
Osmotic Pressure
Types of Osmotic Solutions
Answer
Membrane Transport: Osmosis
Movement of a solvent (e.g., water) across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. Form of passive transport.
Osmotic Pressure: Pressure required to prevent the movement of water across a semipermeable membrane through osmosis.
Types of Osmotic Solutions:
- Hypertonic Solution: Solute concentration outside the cell is higher than inside the cell, so water moves by osmosis out of the cell and into the external medium. Causes the cell to shrink or crenate.
- Isotonic Solution: Solute concentrations are the same inside and outside the cell, no net movement of water across the membrane.
- Hypotonic Solution: Solute concentration inside the cell is higher than outside the cell, so water moves by osmosis into the cell. Causes the cell to swell.
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Card 317
Membrane Transport: Mechanisms
Passive Transport
Simple Diffusion
Facilitated Diffusion
Active Transport
Group Translocation
Answer
Membrane Transport: Mechanisms
Passive Transport: Movement of substances across a membrane that does not require energy input (i.e., ATP). Includes simple diffusion, facilitated diffusion, and osmosis.
Simple Diffusion: Movement of molecules down a concentration gradient, from an area of high concentration to low concentration.
Facilitated Diffusion: Movement of polar or charged molecules using the help of a carrier protein or channel protein in the membrane, down a concentration gradient.
Active Transport: Use of energy (i.e., ATP) to move molecules across the membrane against a concentration gradient from an area of low concentration to an area of high concentration.
Group Translocation: Chemical alteration of a substance as it is transported into the cell. Only occurs in prokaryotic cells.
Card 318
Endosymbiotic Theory: Supporting Evidence
DNA
Types of Ribosomes
Relative Size
Division
Answer
Endosymbiotic Theory: Supporting Evidence
Prokaryotes
Mitochondria
Chloroplasts
Eukaryotes
DNA
Circular
Circular
Circular
Linear
Type of Ribosomes
70S, with 30S and 50S subunits
70S, with 30S and 50S subunits
70S, with 30S and 50S subunits
80S, with 40S and 60S subunits
Relative Size
Small
Small, like prokaryotes
Small, like prokaryotes
Larger than prokaryotes
Division
Binary fission
Binary fission
Binary fission
Mitosis
The composition of the inner membrane of mitochondria and chloroplasts is similar to prokaryotic plasma membranes, while the composition of the outer membrane is similar to eukaryotic plasma membranes.
Card 319
Endosymbiotic Theory
Mitochondria
Chloroplasts
Answer
Endosymbiotic Theory
Theory that explains how some organelles in eukaryotes evolved from prokaryotes.
Mitochondria: Originally arose through an endosymbiotic event in which a bacterium capable of aerobic cellular respiration was taken up by phagocytosis into a host cell and remained as a viable intracellular component.
Chloroplasts: Originally arose through an endosymbiotic event in which a bacterium capable of photosynthesis was taken up by phagocytosis into a host cell and remained as a viable intracellular component.
Card 320
Eukaryotes: Cell Components
Flagella
Cilia
Answer
Eukaryotes: Cell Components
Flagella: Flexible structures used for locomotion, in a whip-like fashion. Composed of a complex of microtubules (i.e., long, hollow tubes made of the protein tubulin) surrounded by the plasma membrane. Microtubules are arranged in a 9 + 2 array (i.e., 9 pairs of microtubules surrounding a central pair of microtubules).
Cilia: Structures found only in eukaryotes. Used for locomotion or to move particles past or into cells (e.g., cilia in the respiratory tract move debris out of the lungs). Structurally similar to flagella, but are shorter and cover the entire surface of the cell.
Eukaryotes: Cell Components
Plasma Membrane: Bilayer composed mainly of phospholipids (like prokaryotes), but with the addition of cholesterol. Cholesterol regulates membrane fluidity and rigidity, as well as water permeability. Also contains glycolipids and glycoproteins, which are important in cell-to-cell communication.
Cell Wall: Structure that surrounds the plasma membrane and protects the cell in fungi, algae, and plants. Made of a variety of materials (e.g., cellulose, chitin, silica).
Animal and protozoan cells do not contain a cell wall.
Extracellular Matrix: Network of proteins and carbohydrates secreted by eukaryotic cells without a cell wall. Protects the cell, allows for attachment, and transmits signals from outside the cell to the inside.
Eukaryotes: Cell Components
Mitochondria: Large, complex organelles where aerobic cellular respiration occurs. Contain an outer membrane and inner membrane folded into cristae. Mitochondrial matrix (i.e., space inside the inner membrane) contains mitochondrial DNA, ribosomes, and metabolic enzymes.
Chloroplasts: Organelles where photosynthesis occurs in plant and algae cells. Contain an outer membrane, inner membrane, and a thylakoid membrane system. Stroma is the gel-like fluid inside the inner membrane. Thylakoids are arranged in stacks called grana. The thylakoid membrane contains chlorophyll (i.e., pigment that absorbs light).
Eukaryotes: Cell Components
Vacuoles: Membrane-bound organelles that have a variety of functions in the cell (e.g., storage of waste products, maintenance of water balance).
Lysosomes: Membrane-bound organelles containing digestive enzymes. Break down particles (e.g., bacteria, cellular debris).
Peroxisomes: Membrane-bound organelles that produce hydrogen peroxide and carry out oxidative reactions. Also involved in lipid biosynthesis.
Card 324
Eukaryotes: Cell Components
Endomembrane System
Endoplasmic Reticulum (ER)
Golgi Apparatus
Answer
Eukaryotes: Cell Components
Endomembrane System: System of membranous structures (e.g., nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles) involved in the synthesis and movement of materials in a eukaryotic cell.
Endoplasmic Reticulum (ER): Interconnected tubules and cisternae (i.e., flattened sacs) with a single lipid bilayer.
- Rough ER: Studded with ribosomes on the outer surface. Involved in protein synthesis.
- Smooth ER: No ribosomes. Involved in lipid synthesis, detoxification of toxic substances, and carbohydrate metabolism.
Golgi Apparatus: Series of stacked membranous disks. Serves as a distribution center. Processes proteins and lipids received from the ER, often adding carbohydrates to them (i.e., forming glycoproteins and glycolipids). Transport vesicles with the modified proteins or lipids pinch off from the Golgi apparatus and travel to their final destination (e.g., incorporation into the plasma membrane, formation of lysosomes, or secretion out of the cell).
Eukaryotes: Cell Components
Cytoplasm: Everything between the plasma membrane and nuclear envelope. Includes a gel-like substance (cytosol) and the structures suspended in it.
Cytoskeleton: Matrix of microfilaments, intermediate filaments, and microtubules in the eukaryotic cytoplasm. Provides structural support and assistance in transporting substances throughout the cell.
Centrosomes: Microtubule organizing centers in animal cells, important in cell division. Each is composed of two centrioles, and each centriole contains nine triplets of microtubules held together by proteins.
Ribosomes: Structures responsible for protein synthesis. Eukaryotic ribosomes are referred to as 80S ribosomes, based on sedimentation rate. Each ribosome is composed of a small 40S subunit and a large 60S subunit. Eukaryotic ribosomes can be freely floating in the cytosol or membrane- bound. Mitochondria and chloroplasts contain 70S ribosomes (i.e., same as prokaryotic cells, a key piece of evidence supporting endosymbiotic theory).
Eukaryotes: Nucleus
Organelle that contains the cell's DNA, organized in multiple linear chromosomes. Controls all cellular activities.
Nucleosome: Basic repeating structural unit of chromatin composed of DNA wrapped around a histone core.
Chromatin: Fibrous complex consisting of repeating units of nucleosomes.
Chromosomes: Highly condensed and tightly coiled chromatin that forms in a cell undergoing nuclear division.
Nucleolus: Site of ribosomal RNA synthesis in the nucleus.
Nuclear Envelope: Double membrane that surrounds the nucleus.
Nuclear Pores: Channels in the nuclear membrane that control movement of materials in and out of the nucleus.
Card 327
Eukaryotes: Cell Components
Illustration
Answer
Eukaryotes: Cell Components
Card 328
Prokaryotes: Flagella Movement
Taxis
Run
Tumble
Answer
Prokaryotes: Flagella Movement
Taxis: Movement of a microbe in response to an external stimulus.
- Chemotaxis: Movement in response to a chemical stimulus.
- Phototaxis: Movement in response to light.
- Magnetotaxis: Movement in response to magnetic fields.
Run: Movement of a bacterium in one direction, through counter-clockwise rotation of flagella.
Tumble: Abrupt change in direction, through clockwise rotation of flagella.
Purposeful movement towards an attractant results in ↑ runs and ↓ tumbles.
Card 329
Prokaryotes: Flagella Arrangements
Illustration
Answer
Prokaryotes: Flagella Arrangements
Card 330
Prokaryotes: Flagella
Parts of a Flagellum
Arrangements of Flagella
Answer
Prokaryotes: Flagella
Structures that allow cells to move in aqueous environments, in a propeller-like fashion. Not enclosed by a plasma membrane.
Parts of a Flagellum:
- Basal Body: "Motor", anchors the flagellum to the cell wall and plasma membrane.
- Hook: Connects the basal body to the filament.
- Filament: Structure that propels the organism, composed of flagellin protein.
Arrangements of Flagella:
- Atrichous: Bacteria without flagella.
- Monotrichous: Single flagellum at one pole.
- Amphitrichous: Flagella at both poles of the cell.
- Lophotrichous: A tuft of flagella at one pole.
- Peritrichous: Flagella covering the entire cell.
Lophotrichous = Lop-sided!
Prokaryotes: Cell Components
Glycocalyx: Sugar coat surrounding the exterior of the cell. Allows cells to adhere to surfaces.
- Capsule: Organized, firmly attached.
- Slime Layer: Unorganized, loosely attached. Aids in the formation of biofilms.
Bacteria with capsules have increased pathogenicity as the capsule allows for evasion from the host's immune system (e.g., avoidance of phagocytosis).
Fimbriae/Pili: Protein appendages that enable the cell to attach to other surfaces and cells. Fimbriae are shorter and more numerous, whereas pili are longer and less numerous.
The F pilus is a specific type of pilus that allows for the transfer of DNA between bacterial cells. Also called a sex pilus or conjugation pilus.
Prokaryotes: Bacterial Cell Walls
Structure that surrounds the plasma membrane and protects the cell from the outside environment.
Peptidoglycan: Major component of the bacterial cell wall. Composed of long chains of alternating NAG and NAM sugar molecules, cross-linked by polypeptide bridges.
Gram-Positive Cell Walls: Consist of many layers of peptidoglycan that are embedded with teichoic acid (TA) and lipoteichoic acid.
Gram-Negative Cell Walls: Consist of a thin layer of peptidoglycan and no teichoic acid.
-
- Contains an outer membrane, a second phospholipid bilayer external to the peptidoglycan layer.
- The space between the inner and outer membrane is the periplasmic space.
- The outer membrane contains porins (i.e., channels) that permit certain substances into the cell.
- The outer membrane contains lipopolysaccharide (LPS), which consists of Lipid A (endotoxin), core polysaccharides, and O-polysaccharides.
Acid-Fast Cell Walls: Contain an external layer of mycolic acid.
Card 334
Prokaryotes: Plasma Membrane
Illustration
Answer
Prokaryotes: Plasma Membrane
Card 335
Prokaryotes: Plasma Membrane
Structure
Fluid Mosaic Model
Answer
Prokaryotes: Plasma Membrane
Thin layer composed primarily of phospholipids that encloses a cell's cytoplasm. Provides selective permeability, allowing certain materials to enter or exit the cell.
Small, non-polar molecules (e.g., O2, CO2) are able to diffuse freely across the plasma membrane. Bilayer is impermeable to larger, polar molecules and ions.
Structure:
- Composed of a phospholipid bilayer. Each phospholipid molecule has a polar head (hydrophilic phosphate group) and 2 nonpolar tails (hydrophobic fatty acids).
- Proteins are embedded in the bilayer and carry out specific membrane functions (e.g., transmembrane proteins selectively transport molecules).
- Glycoproteins (i.e., proteins attached to carbohydrates) and glycolipids (i.e., lipids attached to carbohydrates) extend out from the surface of the cell and allow for cell-to-cell communication.
Membrane has the consistency of oil. It is not a solid structure!
Fluid Mosaic Model: Ability of components of the membrane (e.g., phospholipids, protein) to move freely within the membrane.
Prokaryotes: Vegetative Cells & Endospores
Vegetative Cell: Active form of a cell (i.e., metabolizes, reproduces). Seen when environmental conditions are favorable.
Endospore: Dormant (i.e., metabolically inactive) structure that protects the bacterial genome when environmental conditions are unfavorable.
Sporulation: Process in which a vegetative cell produces an endospore. Typically begins when environmental conditions become unfavorable. Cell replicates its DNA. A septum is created and divides the cell asymmetrically, separating the two copies of DNA into a mother cell and a forespore (which becomes the endospore). Mother cell lyses, releasing the endospore.
Germination: Process in which an endospore returns to a vegetative state. Occurs when environmental conditions improve.
Prokaryotes: Cell Components
Cytoplasm: Everything contained within the plasma membrane. Includes a gel-like substance (cytosol) and the structures suspended in it.
Nucleoid: Region in a prokaryotic cell that contains genetic material. Not bound by a nuclear membrane.
Plasmids: Circular, double-stranded DNA molecules outside the chromosome. Often provide an advantage to the cell (e.g., antibiotic resistance).
Ribosomes: Structures responsible for protein synthesis. Composed of protein and specialized ribosomal RNAs. Prokaryotic ribosomes are referred to as 70S ribosomes, based on sedimentation rate. Each ribosome is composed of a small 30S subunit and a large 50S subunit.
Inclusions: Structures in the cytoplasm that store excess nutrients (e.g., carboxysomes, gas vacuoles).
Card 339
Prokaryotes: Cell Components
Illustration
Answer
Prokaryotes: Cell Components
Card 340
Prokaryotes: Bacilli Arrangements
Single Bacillus
Diplobacilli
Streptobacilli
Palisades
Answer
Prokaryotes: Bacilli Arrangements
Single Bacillus: Single rod
Diplobacilli: Pairs
Streptobacilli: Chain
Palisades: Fence-like arrangement
Prokaryotes: Cocci Arrangements
Diplococci: Pairs
Streptococci: Chains
Tetrads: Groups of 4
Sarcinae: Cubelike groups of 8
Staphylococci: Grape-like clusters
Endospore Stain
Differential staining technique used to visualize bacterial endospores.
Procedure (Schaeffer-Fulton Method):
- Apply primary stain (malachite green) to heat-fixed slide, steam for 5 minutes.
- Rinse the slide with decolorizer (water).
- Apply counterstain (safranin).
- Observe with oil immersion lens.
Interpretation: Endospores will be green. Vegetative cells will be pink.
Rationale:
- Heating allows the malachite green to penetrate the spore wall and bind to peptidoglycan.
- After cooling, the spore wall becomes less permeable, and is therefore not decolorized with water. However, the vegetative cells are easily decolorized and counterstained.
Card 344
Capsule Stain
Procedure
Interpretation
Rationale
Answer
Capsule Stain
Differential staining technique used to identify microbes that have a capsule.
Procedure (Anthony's Capsule Stain):
- Prepare the slide and allow to air dry (do not heat fix).
- Apply 1% primary stain (crystal violet), allow it to remain for 2 minutes.
- Apply 20% copper sulfate. Air dry, do not blot.
- Observe with oil immersion lens.
Interpretation: Bacterial cell and background appear violet. Capsules appear as light blue or white halos. No halos = no capsules.
Rationale:
- Crystal violet stains both the bacterial cell and capsule.
- The capsule is non-ionic (unlike the bacterial cell), so the primary stain will adhere to but not bind to the capsule.
- Copper sulfate serves as a decolorizing agent and counterstain, removing and replacing crystal violet in the capsule only.
Acid-Fast Stain
Differential staining technique used to differentiate cells that have mycolic acid in their cell walls (i.e., acid-fast bacteria).
Procedure (Ziehl-Neelsen Method):
- Apply primary stain (carbolfuchsin) to heat-fixed slide and steam for 5 minutes.
- Rinse slide with decolorizing agent (acid-alcohol).
- Apply counterstain (methylene blue).
Interpretation: Acid-fast bacteria appear pink/red. Non-acid-fast bacteria appear blue.
Rationale:
- Carbolfuchsin stains all cells pink/red. It is lipid-soluble and contains phenol, which helps it penetrate mycolic acid-containing cell walls.
- The decolorizer strips the stain from cells that do not contain mycolic acid, but does not penetrate cell walls containing mycolic acid.
- The decolorized, non-acid-fast cells take up the methylene blue.
Card 346
Gram Stain
Rationale
Answer
Gram Stain
Rationale:
- Gram-positive cells have a thick layer of peptidoglycan in the cell wall. When the decolorizing agent is added, it dehydrates and collapses the peptidoglycan layer and traps the crystal violet and iodine complexes inside the cell.
- Gram-negative cells have a thin layer of peptidoglycan, along with an outer membrane containing lipopolysaccharide. The decolorizing agent disrupts the lipopolysaccharide layer, and the thin peptidoglycan layer cannot retain the crystal violet and iodine complexes.
It is best to use fresh bacterial cultures for Gram staining, as older bacteria have cell wall damage which may cause them to appear Gram-negative when they are actually Gram-positive.
Card 347
Gram Stain
Illustration
Answer
Gram Stain
Card 348
Gram Stain
Procedure
Interpretation
Answer
Gram Stain
Differential staining technique used to differentiate bacterial cells based on cell wall type (i.e., Gram-positive or Gram-negative).
Procedure:
- Apply primary stain (crystal violet) to the heat fixed slide. This gives
all cells a purple color.
- Apply mordant (iodine) to "set" the stain. Complexes form between the
crystal violet stain and iodine.
- Apply decolorizing agent (e.g., ethanol, acetone). Purple dye is
retained in cells with a thick peptidoglycan layer, but dye is washed out
of cells with a thin peptidoglycan layer.
- Apply counterstain (safranin). This stains the decolorized cells pink,
but is less noticeable in cells that retained the crystal violet stain.
Interpretation: Gram-positive bacteria appear purple. Gram-negative bacteria appear red/pink.
Differential Stains
Gram Stain: Used to differentiate bacterial cells based on cell wall type (i.e., Gram-positive or Gram-negative).
Acid-Fast Stain: Used to differentiate bacteria that contain mycolic acid in their cell walls (e.g., Mycobacteria).
Endospore Stain: Used to visualize endospores (i.e., structures in bacterial cells that allow for survival in harsh conditions).
Capsule Stain: Used to identify microorganisms that have a capsule (i.e., protective outer structure that contributes to a microbe's virulence).
Flagella Stain: Used to visualize flagella (i.e., tail-like structures used for locomotion).
Dyes & Stains
Chromophore: Substance that absorbs and emits certain colors of light.
Basic Dye: The chromophore is a positively charged ion in the stain, which is absorbed by the organisms to be examined. This positive stain is attracted to the negatively-charged cell, staining the cell itself.
Examples: Crystal violet, methylene blue, safranin.
Acidic Dye: The chromophore is the negatively charged ion in the stain, which is not absorbed by the organisms to be examined. This negative stain is repelled by the negatively-charged cell, thus staining the background vs. the cell.
Examples: Congo red, nigrosin.
Simple Stain: Use of a single dye to visualize size, shape, and arrangement of cells.
Differential Stain: Use of multiple dyes to differentiate organisms within a specimen or different structures of a single organism.
Card 351
Preparing Specimens for Light Microscopy
Wet Mount
Fixation
Answer
Preparing Specimens for Light Microscopy
Wet Mount: Specimen is placed on the slide in a drop of liquid and covered with a coverslip.
Fixation: Process of attaching cells to a slide using heat or chemicals, which kills the microorganisms in the specimen. Prior to fixation, a smear is made by spreading a thin layer of the specimen over a slide and allowing it to air dry.
- Heat Fixation: Specimen is briefly heated over a heat source (e.g., bunsen burner).
- Chemical Fixation: Specimen is treated with a chemical agent (e.g., formaldehyde).
Card 352
Microscopes
Fluorescence
Confocal
Electron
Scanning Probe
Answer
Microscopes
Fluorescence: Fluorochromes (fluorescent dyes) in the organism absorb energy from the light source and emit visible light.
Confocal: Uses a laser to scan one plane of the specimen at a time. Scans are used to construct a computer-generated 3D image. Good for visualizing complex structures (e.g., biofilms).
Electron: Uses short-wavelength electron beams instead of light, and electromagnets instead of lenses, providing higher magnification and resolution. Occurs in a vacuum, so cannot be used with living cells. Good for visualizing viruses.
Scanning Probe: Uses very precise probes over a specimen's surface, allowing the computer to generate an extremely detailed 3D image. Can observe individual atoms.
Microscopes
Darkfield: Contains an opaque disk between the illuminator and condenser lens. Produces a bright image on a dark background. Used to observe living, unstained organisms.
Phase-Contrast: A special condenser splits the light beam. Direct and refracted light are combined to create high contrast images. Used to observe internal structures of living, unstained organisms.
Differential Interference Contrast: Uses polarized light that is split into two beams by a prism, making the image appear 3D. Used for living, unstained organisms.
Brightfield Microscope
Most common type of microscope. Uses two or more lenses to produce a dark image on a bright background. Requires staining of most organisms to increase contrast.
Illuminator: Light source.
Diaphragm: Adjusts the amount of light that hits the specimen.
Condenser Lens: Focuses light rays on the specimen.
Stage: Platform that holds the specimen slide.
Objective Lens: Lens closest to the specimen. Magnification ranges from 4x to 100x.
Nosepiece: Used to rotate between different objective lenses.
Ocular Lens: Lens closest to the eye (i.e., eyepiece). Provides 10x magnification.
Coarse Focusing Knob: Used for large scale movements with 4x and 10x objective lenses.
Fine Focusing Knob: Used for small scale movements, especially with 40x or 100x objective lenses.
Total Magnification = Objective lens magnification x ocular lens magnification.
Light & Microscope Terminology
Refraction: Change in the direction of light waves as they enter a new medium of different density.
Refractive Index: Light-bending ability of a medium.
Lens: Medium with a curved surface that refracts and focuses light to produce an image.
Magnification: Ability of a lens to enlarge an image.
Resolution: Ability to distinguish two separate points or objects.
Numerical Aperture: Ability of a lens to gather light. ↑ Numerical aperture = ↑ Resolution.
Contrast: The ability to distinguish different parts of a specimen.
Oil Immersion Lens: Lens used with a drop of oil between the specimen and lens. Improves resolution at high magnification.
Oil has a similar refractive index to glass, which decreases light refraction (as compared to air), increasing resolution.
Chemistry Review: Nucleic Acids
Macromolecules composed of long chains of nucleotides. Each nucleotide consists of a 5-carbon sugar, phosphate group, and nitrogenous base.
DNA: A double-stranded molecule composed of nucleotides that serves as the genetic material of all living organisms. The 5-carbon sugar is deoxyribose, and the nitrogenous bases include adenine (A), guanine (G), cytosine (C), and thymine (T).
RNA: A single-stranded molecule composed of nucleotides that functions in protein synthesis. The 5-carbon sugar is ribose, and the nitrogenous bases include adenine (A), guanine (G), cytosine (C), and uracil (U).
Chemistry Review: Lipids
A large, diverse group of hydrophobic macromolecules composed primarily of carbon and hydrogen.
Fatty acids: Long-chain of hydrocarbons with a carboxylic acid functional group.
- Unsaturated Fatty Acids: Contain hydrocarbon chains with at least one double bond. Generally liquid at room temperature.
- Saturated Fatty Acids: Contain hydrocarbon chains with only single bonds; therefore, they are 'saturated' with hydrogens. Generally solid at room temperature.
Triglycerides: Composed of three fatty acids linked to a glycerol molecule.
Phospholipids: A molecule with a hydrophilic region composed of a phosphate group and glycerol, and a hydrophobic region composed of two fatty acids.
Sterols: Complex ringed molecules that function to strengthen cell membranes (e.g., cholesterol) or function as hormones (e.g., testosterone).
Chemistry Review: Carbohydrates
Macromolecules composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.
Monosaccharide: The simplest carbohydrate (i.e., a simple sugar), usually consisting of 3 - 7 carbons (e.g., glucose, fructose, ribose). They are the building blocks for more complex carbohydrates.
Disaccharide: A carbohydrate formed by the bonding of two monosaccharides (e.g., sucrose, lactose, maltose).
Polysaccharide: A chain of hundreds of monosaccharides bonded together. Often function in energy storage or structural support (e.g., starch, glycogen, cellulose, chitin).
Chemistry Review: Proteins
Macromolecules composed of long chains of amino acids. Each amino acid is composed of a hydrogen atom, carboxyl group, amino group, and a side chain attached to an ɑ-carbon.
Primary Structure: Sequence of amino acids linked together to form a polypeptide chain.
Secondary Structure: Folding of a section of the polypeptide chain into ɑ-helices or β-pleated sheets through hydrogen bonding between carboxyl and amino groups of nearby amino acids.
Tertiary Structure: Three dimensional shape determined by interactions between side chains in the polypeptide (e.g., disulfide bridges, hydrogen bonds, ionic bonds).
Quaternary Structure: Formed from side chain interactions between 2 or more polypeptides. Only some proteins have a quaternary structure (e.g., hemoglobin consists of 4 polypeptides).
Card 361
Chemistry Review: Macromolecules
Four Major Macromolecules
Functions in the Body
Answer
Chemistry Review: Macromolecules
Macromolecule
Functions in Body
Proteins
Enzymes, hormones, antibodies, cell structure, transport and storage.
Carbohydrates
Energy production and storage, structural support, component of DNA and RNA.
Lipids
Energy storage, insulation, hormones, component of cell membranes.
Nucleic acids
Storage and transfer of genetic information.
Card 362
Chemistry Review: pH Scale
Illustration
Answer
Chemistry Review: pH Scale
Card 363
Chemistry Review: pH
pH scale
Acid
Neutral
Base
Answer
Chemistry Review: pH
The measure of hydrogen ion (H+) concentration in a given solution. It is calculated as the negative logarithm of the hydrogen ion concentration. pH = - log [H+].
pH Scale: A scale with a range of 0 - 14 that represents the pH of a solution. A change of one unit on the pH scale represents a 10-fold change in the hydrogen ion concentration.
Acid: Any substance that donates H+ into a solution. pH +] > [OH-].
Neutral: pH = 7; [H+] = [OH-].
Base (Alkaline): Any substance that removes H+ from a solution. pH > 7; [H+] -].
[H+] = Concentration of hydrogen ions. [OH-] = Concentration of hydroxide ions.
Card 364
Chemistry Review: Water
Illustration:
- Hydrogen Bonding Between Water Molecules
Answer
Chemistry Review: Water
Card 365
Chemistry Review: Water
Solvent
Solute
Hydrophilic
Hydrophobic
Answer
Chemistry Review: Water
A polar molecule composed of two hydrogens and one oxygen, with a slight positive charge (δ+) on each hydrogen and a slight negative charge (δ-) on the oxygen.
Solvent: A substance that is capable of dissolving another substance (i.e., interacting via hydrogen bonds). Water is an excellent solvent.
Solute: Substance that is being dissolved.
Hydrophilic: A polar, 'water-loving' molecule that can form hydrogen bonds with water and can be dissolved in water (e.g. sugars).
Hydrophobic: A nonpolar, 'water-fearing' molecule that cannot form hydrogen bonds with water and cannot be dissolved in water (e.g. oil, fats).
I am in love with Phil! Hyrophilic = water-loving.
A small percentage of water molecules may dissociate into composite ions (i.e., H+, OH-).
Card 366
Chemistry Review: Chemical Bonds
Covalent bond
Ionic bond
Hydrogen bond
Answer
Chemistry Review: Chemical Bonds
Covalent Bond: A bond that results from the sharing of electrons between atoms. They are the strongest and most common bonds in living organisms.
- Nonpolar Covalent: Electrons are shared equally between atoms because there is no difference in electronegativity (e.g., C-C, C-H).
- Polar Covalent: Electrons are not shared equally between atoms; they are pulled closer to one atom than the other due to a slight difference in electronegativity (e.g., O-H, N-H, O-C, N-C).
Ionic Bond: A bond between ions, resulting from the attraction between cations and anions (e.g., Na+Cl-).
Hydrogen Bond: A weak attractive force between a weakly positive hydrogen atom on one molecule and a weakly negative oxygen, nitrogen, or fluorine atom on another molecule. No electrons are gained, lost, or shared (e.g., water, proteins, DNA).
Card 367
Chemistry Review: Atoms & Ions
Electronegativity
Uncharged Atom
Ion
Cation
Anion
Answer
Chemistry Review: Atoms & Ions
Electronegativity: Measure of an atom's ability to pull shared electrons towards itself. On the periodic table, electronegativity generally decreases down a group, and increases across the table from left to right.
Uncharged Atom: An atom that has no net charge due to an equal number of protons and electrons. # Electrons = # Protons.
Ion: An atom that has a net charge, either positive or negative, due to an unequal number of protons and electrons.
Cation: Positive ion. Forms when an atom loses electrons to a more electronegative atom. Carries a positive charge. # Electrons
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Anion: Negative ion. Forms when an atom gains electrons from a less electronegative atom. Carries a negative charge. # Electrons > # Protons.
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Chemistry Review: Atomic Structure
Proton
Electron
Neutron
Answer
Chemistry Review: Atomic Structure
Proton: A positively-charged particle found in the nucleus of an atom. A proton has a mass of 1 atomic mass unit and a charge of +1. The number of protons defines the identity of an element.
Electron: A negatively-charged particle found traveling in the space around the nucleus of the atom in an energy shell. An electron has a negligible mass and a charge of -1. The number of electrons in the outermost shell (i.e., valence electrons) determines the chemical properties of the atom.
Neutron: A neutrally-charged particle found in the nucleus of an atom. A neutron has a mass of 1 atomic mass unit and a charge of 0.
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Viruses
Key Characteristics
Answer
Viruses
Key Characteristics:
- Acellular infectious agents.
- Consist of DNA or RNA (not both), surrounded by a protein coat.
- Obligate intracellular parasites. Can only reproduce within a host cell by "hijacking" the host's cellular mechanisms.
- Inert outside of a living host.
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Fungi
Key Characteristics
Types
Answer
Fungi
Key Characteristics:
- Unicellular or multicellular eukaryotes.
- Cell wall composed of chitin.
- Reproduce sexually or asexually.
- Nonphotosynthetic.
Types:
- Yeast: Unicellular. Some are beneficial (e.g., baker's yeast), some are pathogenic (e.g., Candida spp.).
- Mold: Multicellular. Made of long filaments (i.e., hyphae) that form colonies (i.e., mycelia). Some produce mycotoxins and are associated with allergies and disease. Penicillium mold is used to make penicillin.
- Dimorphic Fungi: Grow as mold at 25°C (77°F), and as a yeast at 37°C (98.6°F).
Mold in the Cold, Yeast in the Heat.
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Parasites
Key Characteristics
Answer
Parasites
Key Characteristics:
- Unicellular or multicellular eukaryotes.
- Rely on other organisms for nutritional needs.
- Endoparasites live inside their hosts, ectoparasites live outside
their hosts.
- Three main classes of parasites that cause disease in humans:
- Helminths: Large multicellular endoparasites (e.g., flatworms, roundworms).
- Protozoa: Unicellular organisms (e.g., Giardia, Plasmodium).
- Ectoparasites: Organisms that attach or burrow into the skin (e.g., ticks, fleas, lice, mites).
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Algae
Key Characteristics
Answer
Algae
Key Characteristics:
- Unicellular or multicellular eukaryotes.
- Reproduce sexually or asexually.
- Cell walls composed of cellulose.
- Live in aquatic environments.
- Photosynthetic.
- Some algae can produce toxins under certain environmental conditions.
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Protozoa
Key Characteristics
Answer
Protozoa
Key Characteristics:
- Unicellular eukaryotes.
- Reproduce sexually or asexually.
- Some are free-living, some are parasitic.
- Most are non-photosynthetic, except for the genus Euglena.
- Some are pathogenic to humans.
- Movement enabled by:
- Pseudopods: "False feet".
- Flagella: Long, whip-like structures.
- Cilia: Hair-like structures.
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Archaea
Key Characteristics
Answer
Archaea
Key Characteristics:
- Unicellular prokaryotes.
- Cell walls lack peptidoglycan.
- Not pathogenic to humans.
- Able to live in extreme environments.
- Examples:
- Methanogens: Live in anaerobic habitats (e.g., digestive tract of animals). Produce methane as a waste product from respiration.
- Halophiles: Live in extremely salty environments.
- Thermophiles: Live in extremely hot environments.
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Bacteria
Key Characteristics
Answer
Bacteria
Key Characteristics:
- Unicellular prokaryotes.
- Cell wall composed of peptidoglycan.
- Reproduce by binary fission.
- Most are harmless, but some are pathogenic (i.e., disease-causing) to humans.
- Photosynthetic or non-photosynthetic.
- Movement may be enabled by flagella.
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Prokaryotes vs. Eukaryotes
Key Differences
Answer
Prokaryotes vs. Eukaryotes
Prokaryotes
Eukaryotes
Small (0.2 - 2 micrometers).
Large (10-100 micrometers).
DNA is not enclosed in a nuclear membrane and is located in the nucleoid region.
DNA is enclosed in a nuclear membrane and is located in the nucleus.
Singular, circular chromosome.
Multiple, linear chromosomes.
Lack organelles.
Contain organelles.
Divide by binary fission.
Divide via mitosis.
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Phylogeny
Phylogenetic Tree of Life
Answer
Phylogeny
Study of evolutionary relationships between organisms. The phylogenetic tree of life (below) depicts the descent of different organisms from a common ancestor.
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Classification of Organisms
Three Domain System
Acellular Infectious Agents
Answer
Classification of Organisms
Three Domain System: System for classifying organisms based on differences in the cell's RNA, cell membrane structure, and sensitivity to antibiotics.
- Bacteria: Prokaryotic cells. Cell walls contain peptidoglycan.
- Archaea: Prokaryotic cells. Cell walls do not contain peptidoglycan.
- Eukarya: Eukaryotic cells. For eukarya that do have a cell wall, the cell wall does not contain peptidoglycan. Eukarya are subdivided into 4 kingdoms:
- Protists (e.g., protozoa, algae, slime molds).
- Fungi (e.g., yeasts, molds).
- Plants (e.g., mosses, flowering plants).
- Animals (e.g., sponges, worms, insects, fish, birds, mammals).
Acellular Infectious Agents: Infectious particles not composed of cells (e.g., viruses, viroids, prions). Not part of the three domain system.
Taxonomy
Classification of living organisms. Originally developed by Carl Linnaeus.
Taxonomic Hierarchy: Grouping of organisms based on shared characteristics.
- Domain (eukarya, archaea, or bacteria) → Kingdom (applicable to eukarya only) → Phylum → Class → Order → Family → Genus → Species
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Binomial Nomenclature: Two-word naming system for identifying organisms by genus and species. Name is italicized. Genus is capitalized. Species is lowercase. Examples:
- Escherichia coli (E. coli), a bacterium.
- Homo sapiens (H. sapiens), a human.
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Koch's Postulates
Four Postulates
Answer
Koch's Postulates
Set of criteria that establishes whether a specific disease is caused by a specific microbe (i.e., one microbe, one disease).
Suspected pathogen must be present in all diseased organisms, but absent in healthy organisms.
Suspected pathogen must be isolated and grown in a pure culture.
A healthy susceptible organism that is infected with the suspected pathogen must develop the same signs/symptoms as seen in #1.
Pathogen must be re-isolated from the new host and be identical to pathogen from #2.
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History of Microbiology
Germ Theory of Disease
Joseph Lister
Robert Koch
Alexander Fleming
Answer
History of Microbiology
Germ Theory of Disease: Diseases are caused by microorganisms.
Joseph Lister: Applied germ theory of disease to surgery, reducing surgical infections. Treated surgical wounds with phenol (i.e., a chemical disinfectant). Father of antiseptic surgery.
Robert Koch:
- Provided evidence for the germ theory of disease with B. anthracis discovery.
- Developed plate technique for obtaining "pure cultures" (i.e., growth of a single species of a microorganism).
- Developed Koch's postulates.
Alexander Fleming: Discovered penicillin, the first natural antibiotic.
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History of Microbiology
Edward Jenner
Louis Pasteur
Answer
History of Microbiology
Edward Jenner: Laid the foundation for vaccination by demonstrating that inoculation with cowpox protected individuals from smallpox.
Louis Pasteur:
- Disproved spontaneous generation through his swan-neck flask experiment and provided evidence for the concept of biogenesis.
- Discovered that fermentation (i.e., conversion of sugars into alcohol in the absence of air) is caused by microorganisms.
- Showed microbes can be destroyed by heat, a process known as pasteurization.
- Developed vaccines for rabies, fowl cholera, and anthrax.
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History of Microbiology
Robert Hooke
Anton van Leeuwenhoek
Spontaneous Generation
Theory of Biogenesis
Answer
History of Microbiology
Robert Hooke: First to observe larger cells through a microscope. Coined the term "cell". Marked the beginning of cell theory (i.e., all living things are made of cells).
Antonie van Leeuwenhoek: "Father of Microbiology". First to observe live microorganisms through a microscope.
Spontaneous Generation: The idea that life can arise spontaneously from non-living matter.
Theory of Biogenesis: Principle that all living cells arise from pre-existing cells.