Term
| How does EPEC bind to microvilli on the surface of intestinal epithelium? |
|
Definition
|
|
Term
| How are pedestals formed by the microvilli after EPEC bind to them? |
|
Definition
| Actin polymerization as a result of Type III secretion system |
|
|
Term
| What are the symptoms of EPEC? |
|
Definition
| Fever, diarrhea (non-bloody), and/or nausea/vomiting |
|
|
Term
| Is EPEC common in the US? What is the most susceptible population? |
|
Definition
|
|
Term
|
Definition
| Fluids, electrolytes; Breastfeeding protects against it (IgA) |
|
|
Term
| What are the toxins formed by ETEC? |
|
Definition
Heat Labile (LT; aka AB-type) Toxin: increases cAMP causing increase in Cl- ion secretion and watery diarrhea;
Heat Stabile (ST) Toxin: increases cGMP |
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|
Term
|
Definition
|
|
Term
| What is ETEC typically associated with? |
|
Definition
| Traveler's diarrhea; watery diarrhea, NO PMNS or RBCs |
|
|
Term
| What toxin does EHEC produce |
|
Definition
| Vero Toxin (Shiga-like toxin): AB-type toxin that inactivates 28s rRNA |
|
|
Term
| What is the most well studied EHEC strain? |
|
Definition
|
|
Term
|
Definition
| Undercooked hamburger, spinach, lettuce; low infectious dose |
|
|
Term
| What are the symptoms of EHEC? |
|
Definition
| Diarrhea to dysentery; HUS in children; NO fever |
|
|
Term
| How do you identify EHEC? |
|
Definition
| Sorbitol non-fermenter; culture on S-MAC plate: will not grow pink colonies |
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|
Term
| Is antibiotic therapy indicated for EHEC? |
|
Definition
| No, may release toxin and increase risk for HUS |
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|
Term
|
Definition
|
|
Term
| What is pathogenesis of EIEC? |
|
Definition
| Invades intestinal mucosa and spreads from one cell to another forming Actin tail (like Listeria); requires relatively large inoculum |
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|
Term
|
Definition
|
|
Term
| What are the symptoms of EIEC? |
|
Definition
| Watery diarrhea; can progress to dysentery (similar to Shigella) |
|
|
Term
| What is the pathogenesis of EAEC? |
|
Definition
| Bacterial fimbriae allow attachment to epithelia, production of mucous and formation of biofilm |
|
|
Term
| What are the symptoms of EAEC? |
|
Definition
| Persistent watery diarrhea (>14 days); causes Traveler's diarrhea |
|
|
Term
| What are the characteristics of Salmonella? |
|
Definition
| Gram (-) rod; motile; lactose non-fermenter; H2S gas producer |
|
|
Term
| What color colonies would Salmonella grow on MacConkey agar? |
|
Definition
|
|
Term
| What color colonies would Salmonella grow on Hektoen-enteric agar? |
|
Definition
| Black (w/ gas bubble around them) |
|
|
Term
| What are the two most common serotypes of Salmonella? |
|
Definition
| Salmonella typhi (Typhoid fever); Salmonella enteritidis (non-typhoidal gastroenteritis) |
|
|
Term
| What are the antigens of Salmonella? |
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Definition
| O antigen; Flagella (H) antigens; Capsular (Vi) antigen |
|
|
Term
| What are the antigens of E. Coli? |
|
Definition
| O antigen; Flagella (H) antigen; Capsular (K) antigen |
|
|
Term
| What is the pathogenesis of Salmonella? |
|
Definition
| Invades intestinal M cells and macrophages; macrophages ingest bug and are carried elsewhere in body; Peyers patches contain Ags and undergo necrosis |
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|
Term
| How is Salmonella typhi transmitted? |
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Definition
| Fecal-oral transmission from infected carriers; humans only known host; not common in US; low infectious dose |
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|
Term
| What are the symptoms of Salmonella typhi? |
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Definition
| Fever, headache, myalgias, GI distress (diarrhea), rose spots on chest; inflammation of Peyers pacthes --> necrosis; intestinal hemorrhage/perforation; gall bladder infection |
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|
Term
| How is Salmonella enteriditis transmitted? |
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Definition
| Many reservoirs (birds, reptiles) |
|
|
Term
| What are the symptoms of Salmonella eneriditis? |
|
Definition
| Diarrhea (mild to severe); often self-limiting |
|
|
Term
| How do you identify Salmonella typhi? |
|
Definition
|
|
Term
| What are the characteristics of Shigella? |
|
Definition
| Gram (-) rod; non-motile; lactose non-fermenter; non-H2S gas producer |
|
|
Term
| What color colonies would Shigella grow on MacConkey agar? |
|
Definition
|
|
Term
| What olor colonies would Shigella grow on Hektoen-enteric agar? |
|
Definition
|
|
Term
| What are the symptoms of Shigella? |
|
Definition
| Bacillary dysentery; abdominal cramps; fever; WBCs in stool |
|
|
Term
| What is the infectious dose for Shigella? |
|
Definition
| Very low (100-200 cells/CFUs) |
|
|
Term
| What are the 4 most common serotypes of Shigella? Where are they found? What is their pathogenicity? |
|
Definition
S. dysenteriae: most pathogenic; produce Shiga toxin
S. flexneri: most common in developing countries
S. boydi: India
S. sonnei: US, industrialized countries; mildest form |
|
|
Term
| What is the pathogenesis of Shigella? |
|
Definition
| Invade M cells and macrophages but don't leave intestine |
|
|
Term
| What are the characteristics of Yersinia enterocolitica? |
|
Definition
| Gram (-) pleomorphic rod; lactose non-fermenter; grow in cold (4C) |
|
|
Term
| What are the symptoms of Yersinia? |
|
Definition
| Acute enterocolits; mesenteric lymphadenitis (mimics acute appendicitis); mucosal ulcerations (terminal ileum); septicemia (immunocompromised, elderly); transfusion septicemia |
|
|
Term
| What are the characteristics of Campylobacter? |
|
Definition
| Gram (-) curved rod (comma or S shaped); very small; motile; microaerophilic (grows better at 42C) |
|
|
Term
| What media do you need to grow Campylobacter? |
|
Definition
|
|
Term
| What does Campylobacter jejuni most commonly cause? |
|
Definition
| Most common cause of gastroenteritis in US |
|
|
Term
| What is the pathogenesis of Campylobacter? |
|
Definition
| Fecal-oral contaminant of food (especially poultry, fluids - milk/water) |
|
|
Term
| What are the symptoms of Campylobacter? |
|
Definition
| Diarrhea, fever, malaise; associated w/ Guillain-Barre syndrome (serotype O19 of C. jejuni); reactive arthritis |
|
|
Term
| What are the characteristics of Vibrio cholerae and parahemolyticus? |
|
Definition
| Gram (-) curved rods; oxidase (+); facultative anaerobes |
|
|
Term
| What are the chracteristics of E. coli? |
|
Definition
| Gram (-) rods; oxidase (-); facultative anaerobes; lactose fermenters; sorbitol fermenters (except EHEC) |
|
|
Term
| What toxins are associated with some serotypes of Vibrio? |
|
Definition
Classic cholera toxin (AB toxin): B binds to ganglioside GM1 on intstinal epithelia; A activates cAMP pathway causing increased secretion of fluid/electrolytes --> watery diarrhea
Zonula occudens toxin: loosens tight junctions
Accessory cholera toxin: increases fluid secretion |
|
|
Term
| What are the bugs that cause Traveler's diarrhea? |
|
Definition
| ETEC, EAEC, Crytosporidium (Nepal) |
|
|
Term
| What bugs cause invasive diarrhea? |
|
Definition
| EIEC, Salmonella, Shigella, ??? |
|
|
Term
| What are the symptoms of V. cholera? |
|
Definition
| Not invasive; diarrhea (w/ vomiting), colorless/odorless stools w/ mucous (rice water stools) |
|
|
Term
| What is the transmission of Vibrio? |
|
Definition
| Found in marine waters - associated w/ shellfish; high inoculum needed |
|
|
Term
| What are the symptoms of V. parahemolyticus? |
|
Definition
| Invasive; explosive watery diarrhea |
|
|
Term
| What are the characteristics of Clostridium? |
|
Definition
| Gram (+) rods; spore formers; obligate anaerobes |
|
|
Term
| What are the symptoms of C. perfringens? |
|
Definition
| Enteric infections (including gas gangrene); food poisoning if ingest food containing toxin (C. perfringens type A); enteritis necroticans (necrosis; C. perfringens type C) |
|
|
Term
| What condition is most often associated with C. difficile? |
|
Definition
| Pseudomembranous colitis; most common cause of hospital acquired-diarrhea (antibiotic associated) |
|
|
Term
| What is the most likely cource of C. botulinum? |
|
Definition
| Canned food, especially home-canned |
|
|
Term
| What are the symptoms of C. botulinum infection? |
|
Definition
| Muscle paralysis (flaccid paralysis), droopy eyelids, blurred vision, difficulty swallowing, slurred speech |
|
|
Term
| What toxin can be found in meat (especially salted meat) and dairy? |
|
Definition
| Staph aureus enterotoxin = superantigen; T cell polyclonal activator based on particular Vbeta families of the TCR; causes Cytokine storm |
|
|
Term
| What are two toxins associated with B. cereus? |
|
Definition
Heat stabile enterotixin (emetic toxin): causes vomiting; associated w/ fried rice
Heat labile eneterotoxin (E. coli enterotixin like):causes diarrhea; associated w/ meat & vegetables |
|
|
Term
| What is the toxin produced by C. bolulinum? |
|
Definition
| AB toxin: B binds to motor neuron, A inhibits release of ACh |
|
|
Term
| What is the most common cause of infant botulism? |
|
Definition
| Ingestion of C. botulinum endospores in honey |
|
|
Term
| Which hookworm is noted for more likely causing anemia? |
|
Definition
|
|
Term
| What is the method of entry for hookworms into host? |
|
Definition
| Penetrate feet or ankles in water |
|
|
Term
| What is the lifecycle of Strongyloides stercoralis? |
|
Definition
| Enters through skin; travels to lungs; travles up into throat where it is swallowed; develops into adult in intestine; hatch eggs in intestine which can pass in stool (rhabditiform larvae) or penetrate intestinal mucusoa (filariform larvae) |
|
|
Term
| What is the mechanism by which one acquires a hyperinfection from Strongyloides stercoralis? |
|
Definition
| Filariform larvae penetrate intestinal mucosa and enter blood; can result in pneumonia and diarrhea; high risk in someone on immunosuppresants (corticosteroids) |
|
|
Term
| How do you acquire Strongyloides stercoralis? |
|
Definition
| Filariform larvae in soil can penetrate skin of feet |
|
|
Term
| Which form of threadworm is infectious and which is non-infectious? |
|
Definition
| Filariform larvae is infectious (can be in soil or hatched in intestine); rhabditiform larvae is non-infectious |
|
|
Term
| What is the life cycle of Ascaris lumbricoides? |
|
Definition
| Ingest the egg; larvae burrow through intestine and enter blood stream; travel up to lungs and burrow into alveoli; travel up throat and are swallowed back down into intestines where they become adults and start over; can grow to about 1 ft |
|
|
Term
| What worm causes itching as the female travels outside the anus to lay her eggs? |
|
Definition
| Enterobius vermicularis (pinworm) |
|
|
Term
| Which worm has eggs that are football shaped with plugs at the ends and can cause inflammation --> rectal prolapse? |
|
Definition
| Trichuris trichuria (whipworm) |
|
|
Term
| Which worm feeds on bile and can lead to cholangiocarcinoma? |
|
Definition
| Clonorchis sinesis (Chinese liver fluke) |
|
|
Term
| How can you acquire Clonorchis sinesis? |
|
Definition
|
|
Term
| Which bug can you detect with serological testing or presence of operculated eggs in stool? |
|
Definition
| Fasciola hepatica (liver fluke) |
|
|
Term
| What is the life cycle of Fasciola hepatica? |
|
Definition
| Adults live in hepatic bile duct; eggs are relased in stool and eaten by snails; snails can leave them on water plants; will develop into adult in human who ingests water plant |
|
|
Term
| What is the most common cause of mild gastroenteritis in the US? |
|
Definition
|
|
Term
| What are the characteristics of Norovirus? |
|
Definition
| Positive ssRNA, naked icosahedral; member of Calciviridae family |
|
|
Term
| What are the symptoms of Norovirus infection? |
|
Definition
| Mild and self-limiting; watery diarrhea, no RBCs or PMNs in stool |
|
|
Term
| What is the mode of transmission of Norovirus? |
|
Definition
| Fecal-oral; shellfish concentrate virus |
|
|
Term
| What is the treatment for Norovirus gastroenteritis? |
|
Definition
|
|
Term
| What are the chracteristics of Rotavirus? |
|
Definition
| Segmented dsRNA genome, naked icosahedral; member of Reoviridae family |
|
|
Term
| What are the symptoms of Rotavirus? |
|
Definition
| Diarhhea, vomiting, fever; destroys intestinal epithelia, atrophy of villi |
|
|
Term
| What are the characteristics of Adenovirus? |
|
Definition
| dsDNA associated w/ diarrhea |
|
|
Term
| What are the characteristics of Poliovirus? |
|
Definition
| Positive ssRNA naked icosahedral; member of Picornaviridae family |
|
|
Term
| What is the life cycle of Entamoeba histolytica |
|
Definition
| Ingest the cyst; in the intestine cyst becomes trophozoite; troph invades epithelia and phagocytizes RBCs; can travel in the blood to liver |
|
|
Term
| How do you identify Entamoeba histolytica? |
|
Definition
| O&P smear: troph has single nucleus, usually w/ RBCs in it; cyst has four nuclei and is smaller |
|
|
Term
| How do you identify Giardia lamblia? |
|
Definition
| Antigen assay or O&P smear; formed stool would only see cysts w/ 4 nuclei; in watery stool may see trophozoites that are pear-shaped w/ flagella |
|
|
Term
| What are the symptoms of Giardia? |
|
Definition
| Foul-smelling loose watery diarrhea, flatulence, nausea, weight loss |
|
|
Term
| What is the animal reservoir for Giardia? |
|
Definition
|
|
Term
| What protozoan has a large kidney bean-shaped nucleus and doesn't travel outside intestine? |
|
Definition
|
|
Term
| What non-motile protozoan is an opportunistic pathogen that causes watery diarrhea and can be indentified by acid fast stain? |
|
Definition
|
|
Term
| What non-motile protozoan is an opportunistic pathogen in immunocompromised that causes diarrhea and can be identified w/ UV autoflourescence? |
|
Definition
|
|
Term
| Which cestode can lead to the hydatid cyst developing a liver abcess? |
|
Definition
| Echinococcus ganulosus (dog tapeworm) |
|
|
Term
| Which Cestode can lead to anemia due to absorption of vit B12? |
|
Definition
| Diphyllobothrium latum (fish tapeworm) |
|
|
Term
| Which tissue can the larvae of Taenia solium hatch in humans? |
|
Definition
|
|
Term
| Where do the Trematode Schistoma (blood fluke) invade the host? |
|
Definition
| In veins near intestines or bladder |
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