GI Infections 7

Question 1

what is the cytotoxic effect of Shiga toxin

Answer 1

• 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

Question 2

NAD glyochydrolase is a virulence factor for ______

Answer 2

shigella; shuts down ATP production

Question 3

which inflammatory diarrhea causing organisms can also cause reactive arthritis?

Answer 3

• salmonella
• shigella
• yersinia
• campylobacter

“cant see, cant pee, cant climb a tree”

Question 4

4 F’s of shigella

Answer 4

Food, flies, fingers, feces

ways of transmission for fecal oral. route

Question 5

inflammatory diarrhea most commonly affects the _____ intestine

Answer 5

large

Question 6

what are some characteristics of enterobacteriaceae

Answer 6

• facultative anaerobes
• gram NEGATIVE, non spore forming rod shaped abcteria
• motile EXCEPT for Klebsiella and shigella

Question 7

is shigella invasive?

Answer 7

not really; does not invade beyond the lamina propria

Question 8

STEC will cause _______ color in sorbitol MacConkey’s agar

Answer 8

colorless because it does not ferment glucose

Question 9

STEC is also known as EHEC and is associated with ____ (food)

Answer 9

beef patties

Question 10

_____ colored colonies can be seen when rowing STEC on MacConkey’s agar

Answer 10

red-pink colored colonies

Question 11

what are the characteristics of Shiga toxin? what shigella species can this be found in?

Answer 11

• enterotoxic, neurotoxic, cytotoxic

- found in shigella dysenteriae type 1

Question 12

what are some pathogenic mechanisms of EAEC

Answer 12

• adherence
• mucose production → biofilm formation
• cytotoxin production

Question 13

what are 3 life threatening conditions caused by STEC?

Answer 13

1. Hemorrhagic colitis (3 days after ingestion)
2. hemolytic uremic syndrome (5-13 days post diarrhea) and occurs in kids < 5 y/o
3. TTP

Question 14

Shiga toxin is encoded by _____

Answer 14

chromosomal genes

Question 15

shigella ______ is seen in children less than 5 years old and in day care

Answer 15

sonnei (most common)

Question 16

shigella species is broken up into 4 groups based on ______

Answer 16

O antigen

Question 17

how does shigella move from host cell to host cell?

Answer 17

aid of actin filaments; (F actin polymerization)

Question 18

what are the virulence factors of shigella?

Answer 18

• 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

Question 19

phagosome lysis is a characteristic of ______

Answer 19

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

Question 20

what is the enterotoxic effect of the Shiga toxin?

Answer 20

• adheres to small intestine epithelium and blocks absorption of electrolytes, glucose and AA
• watery diarrhea

Question 21

does E. coli ferment lactose?

Answer 21

YES

Question 22

EIEC utilizes ____ associated genes which code for ________

Answer 22

plasmid encoded genes that code for the outer protein that mediates invasion

Question 23

reservoirs of EHEC/STEC is _______

Answer 23

cattle and sheep

Question 24

other than H2S production, what other characteristic can help differentiate between shigella and salmonella

Answer 24

salmonella is motile while shigella is non motile

Question 25

can shigella ferment lactose?

Answer 25

NO

Question 26

shigella ______ is seen in gay men

Answer 26

flexneri

Question 27

EIEC has a low / high infective dose

Answer 27

VERY LOW (as small as 10 organisms)

Question 28

damage to _____ causes the formation of micorthrombi in _____ infection

Answer 28

RBC's; STEC/EHEC infection

Question 29

_____ and _____ and inflammatory diarrhea causing agents THAT DO NOT invade the enterocytes

Answer 29

- EAEC | - STEC

Question 30

Shiga cytotoxin binds to __________ which inhibits protein synthesis and causes cell death

Answer 30

60S ribosomal subunit

Question 31

EIEC is similar to _____

Answer 31

shigella

Question 32

which inflammatory diarrhea causing pathogens can have a complication of glomerulonephritis?

Answer 32

- Shigella - Yersinia - campylobacter

Question 33

shigella is acid labile/stable

Answer 33

stable; salmonella is acid labile

Question 34

STEC produces a ____ encoded cytotoxin (verotoxin)

Answer 34

phage

Question 35

how is shigella spread?

Answer 35

- fecal oral; no known animal reservoir

Question 36

of the enterbacteriacae, which are NON LACTOSE fermenters

Answer 36

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)

Question 37

EHEC produces ____ toxin

Answer 37

Shiga

Question 38

what is the function of AAF (aggregative adherence factor) in _____

Answer 38

EAEC; | it mediates attachment to the intestinal mucosa and triggers host inflammatory response

Question 39

EAEC is characterized by the presence of ________

Answer 39

AAF (aggregative adherence fimbriae)