GI Infections 7 Flashcards
what is the cytotoxic effect of Shiga toxin
- A1B5 structure and the A domain is internalized by receptor mediated endocytosis
- causes irreversible inhibition of the 60S ribosomal subunit → cell death, microvascular damage of intestine and hemorrhage
NAD glyochydrolase is a virulence factor for ______
shigella; shuts down ATP production
which inflammatory diarrhea causing organisms can also cause reactive arthritis?
- salmonella
- shigella
- yersinia
- campylobacter
“cant see, cant pee, cant climb a tree”
4 F’s of shigella
Food, flies, fingers, feces
ways of transmission for fecal oral. route
inflammatory diarrhea most commonly affects the _____ intestine
large
what are some characteristics of enterobacteriaceae
- facultative anaerobes
- gram NEGATIVE, non spore forming rod shaped abcteria
- motile EXCEPT for Klebsiella and shigella
is shigella invasive?
not really; does not invade beyond the lamina propria
STEC will cause _______ color in sorbitol MacConkey’s agar
colorless because it does not ferment glucose
STEC is also known as EHEC and is associated with ____ (food)
beef patties
_____ colored colonies can be seen when rowing STEC on MacConkey’s agar
red-pink colored colonies
what are the characteristics of Shiga toxin? what shigella species can this be found in?
- enterotoxic, neurotoxic, cytotoxic
- found in shigella dysenteriae type 1
what are some pathogenic mechanisms of EAEC
- adherence
- mucose production → biofilm formation
- cytotoxin production
what are 3 life threatening conditions caused by STEC?
- Hemorrhagic colitis (3 days after ingestion)
- hemolytic uremic syndrome (5-13 days post diarrhea) and occurs in kids < 5 y/o
- TTP
Shiga toxin is encoded by _____
chromosomal genes
shigella ______ is seen in children less than 5 years old and in day care
sonnei (most common)
shigella species is broken up into 4 groups based on ______
O antigen
how does shigella move from host cell to host cell?
aid of actin filaments; (F actin polymerization)
what are the virulence factors of shigella?
- O antigen (endotoxin)
- exotoxin: neurotoxin that can cause meningismus, and coma, ulceration
- NAD glycohydrolase: destroys all NAD in human cells → shuts down metabolism → cell death
phagosome lysis is a characteristic of ______
shigella;
binds to M cell → ingested by macrophage/phagosome → phagosome lysis and macrophage apoptosis and replicates in the cytoplasm→ release of IL-1 and PMN transmigration → shigella migrates through disrupted tight junctions
what is the enterotoxic effect of the Shiga toxin?
- adheres to small intestine epithelium and blocks absorption of electrolytes, glucose and AA
- watery diarrhea
does E. coli ferment lactose?
YES
EIEC utilizes ____ associated genes which code for ________
plasmid encoded genes that code for the outer protein that mediates invasion
reservoirs of EHEC/STEC is _______
cattle and sheep
other than H2S production, what other characteristic can help differentiate between shigella and salmonella
salmonella is motile while shigella is non motile
can shigella ferment lactose?
NO
shigella ______ is seen in gay men
flexneri
EIEC has a low / high infective dose
VERY LOW (as small as 10 organisms)
damage to _____ causes the formation of micorthrombi in _____ infection
RBC’s; STEC/EHEC infection
_____ and _____ and inflammatory diarrhea causing agents THAT DO NOT invade the enterocytes
- EAEC
- STEC
Shiga cytotoxin binds to __________ which inhibits protein synthesis and causes cell death
60S ribosomal subunit
EIEC is similar to _____
shigella
which inflammatory diarrhea causing pathogens can have a complication of glomerulonephritis?
- Shigella
- Yersinia
- campylobacter
shigella is acid labile/stable
stable;
salmonella is acid labile
STEC produces a ____ encoded cytotoxin (verotoxin)
phage
how is shigella spread?
- fecal oral; no known animal reservoir
of the enterbacteriacae, which are NON LACTOSE fermenters
ShYPS
-shigella
- yersinia
(above two are non motile non lactose fermenters and non H2S producers)
- Proteus
- Salmonella
(above two are motile, non lactose fermenters, H2S producers)
EHEC produces ____ toxin
Shiga
what is the function of AAF (aggregative adherence factor) in _____
EAEC;
it mediates attachment to the intestinal mucosa and triggers host inflammatory response
EAEC is characterized by the presence of ________
AAF (aggregative adherence fimbriae)
