GI Infections 5 Flashcards
if the patient is only positive for the antibodies to HBs antigen, it is indicative of ______
vaccinated against HBV
what are some incriminated foods for contamination by the B. cereus emetic toxin
rice
_______ has a bacteriophage encoded enterotoxin
Vibrio cholera
what are some common pathogens in the Enterobacteriaceae family?
- E. coli
- Shigella
- Salmonella
- Yersinia
- Klebsiella
- Proteus
pt. has negative surface antigen positive antibodies for surface antigen and has positive iGG for HBc
previous exposure
vibrio cholera has a ______ encoded enterotoxin
bacteriophage
_________ is an E. coli plasmid encoded enterotoxin that has similar function as that of the Cholera toxin
LT enterotoxin
cholera = activates adenylate cyclase
the B subunit binds to ______ on the cell surface
GM1 receptor
what is the difference between the enterotoxin released by E. coli and that released by Vibrio cholera?
- both cause watery diarrhea
- both are AB enterotoxins that bind to GM1 receptor
- E. coli is PLASMID encoded
- Vibrio cholera is BACTERIOPHAGE encoded
which E. coli strain does NOT have LT or ST or CFA? how does it cause watery diarrhea?
- EPEC (enteropathogenic)
- via effacement of the microvilli in the SI
incubation period of someone who just ingested a preformed exotoxin in food:
within hours of eating the food
why is ingestion of antacids a risk factor for developing vibrio cholera infection?
vibrio cholera is acid sensitive so by ↑ the pH of the stomach, then it makes it more likely for the bacteria to survive
describe the structure of the enterotoxins released by E. coli and how they attach
it is a 1A5B toxin (5 peripheral B subunits all attached to one central A subunit)
B subunit binds to GM1 receptor and the A subunit enters the cell and causes the ↑ in cAMP or cGMP
clostridium perfringens is associated with _________ (food)
meat dishes/gravy that have been left out after being heated
Vibrio Cholera is oxidase _______
POSITIVE (E. coli is oxidase negative)
after adhesion, E. coli releases two plasmid-encoded _________:
enterotoxins:
LT: activates adenylate cyclase (similar to cholera)
ST: activates guanylate cyclase
vibrio cholera is a +/- sucrose fermenter
+
what is the mechanism of the ST (heat stable) enterotoxin released by E. coli?
- activates guanylate cyclase
what is the difference between C. perfringens and B. cereus in terms of enterotoxin production
- C. perfringens only produces the toxins once it is inside the SI
- B. cereus can produce the toxin while in the food so you can ingest the toxin but not for C. perfringens
the cholera toxin is similar to the ______ enterotoxin of E. coli
LT (↑ cAMP)
what kind of enterotoxin is produced by C. perfringens?
LT (CPE)
what are some unique features of EPEC?
EPEC does NOT have ST or LT or CFA
EPEC has a large adherence factor plasmid that encodes for bundle forming pili
describe the biology of clostridium perfringens
- gram postive
- large anaerobes
- non motile
- ubiquitous in nature
- spore forming
E. coli has a ________ encoded enterotoxin
plasmid
what is the mechanism of the cause of non inflammatory diarrhea
colonization and release of enterotoxin in SI
what is the cause of the emetic type of bacillus cereus infection
ingestion of food containing PREFORMED ST NEUROTOXIN
the H antigen in E. coli makes up the ______
subunits of the bacterial flagella
gram negative rod that ferments sucrose and mannose but NOT arabinose
Vibrio cholera
how does EPEC colonize and adhere to the SI when it does not have CFA?
EPEC strains carry a large EPEC adherence factor plasmid that encodes bundle forming pili (BFP)
then it effaces the microvilli → loss absorptive surface → watery diarrhea
describe the biology of E. coli catalase: oxidase: agar: does it ferment lactose?
- gram negative bacilli
- facultative anaerobe
- member of normal (commensal) intestinal flora
- catalase positive
- oxidase negative
- lactose fermenter
- grown on MacConkey agar
how does C. perfringens cause watery diarrhea?
- sporulation in the SI
- release of CPE (C. per fringes enterotoxin/ LT)
- cytotoxic activity in which there is pore formation in the membrane
metabolic ________ is a common result of diarrhea
acidosis due to the loss of HCO3
__________ is a bacteria that has cytotoxic activity and causes pore formation leading to watery diarrhea
C. perfringens
describe the biology of Vibrio cholera
motile?
spore forming?
oxidase activity?
- single curved gram NEGATIVE rods
- ”s” shaped
- motile with a single polar flagellum
- non spore forming
- oxidase POSITIVE
which E. coli strain is also known as “infantile diarrhea”
EPEC
ePec: Pediatrics
what is a screening method for cholera in stool samples?
- look for oxidase activity because E. coli does not have oxidase activity while Cholera does
TCBS agar is used for what pathogen?
Vibrio cholera
_____ is grown in MacConkey agar
E. coli
it is a selective media
strains of Vibrio cholera are classified based on ______
O and H antigens
O1 and O139 are most important
describe the biology of bacillus cereus
gram positive
arranged in chains
aerobic
has both emetic toxin and enterotoxin
where can you find bacillus cereus
air, soil, water, and dust
which species of E. coli is the #1 cause of traveller’s diarrhea?
- ETEC (enterotoxigenic E Coli)
how does E. coli attach to and colonize the SI?
-CFA: colonization factor antigens = fimbrae
what is the neurotoxin that is ingested from contaminated rice in ______ infection
ST neurotoxin in B. cereus infection causing emesis
Vibrio cholera can be grown on _________ agar with ______ as the differentiating agent
- thiosulfphate citrate bile salts sucrose (TCBS) agar
- SUCROSE is the differentiating agent → yellow color because cholera ferments sucrose
viral infection usually causes ______ diarrhea
non inflammatory
bundle forming pili is a virulence factor for _____
EPEC
what is the diarrhea enterotoxin in bacillus cereus
LT (↑ cAMP)
fecal leukocytes are NOT found in inflammatory/noninflammatory diarrhea
non inflammatory diarrhea
