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Medicine II: Infectious Disease > GI Infections > Flashcards

Flashcards in GI Infections Deck (48):
1

Most common bacterial causes of acute diarrhea

salmonella, shingella, campylobacter, E. coli

2

Salmonella risk factors

antacid use, prior abx use, depressed immune function

3

How do we get Salmonella

contracted via contaminated food, mostly meat and milk products, undercooked chicken products.

4

Dx of Salmonella

monocytes in the stool (2+ PMNs) (RBCs-rare)

5

Salmonella

A aerobic gram neg. bacillus; motile, does not ferment lactose; acid sensitive

6

How and where does Salmonella infect?

attach to epithelial cells in SI and colon

7

Shingella

gram neg bacillus, nonmotile, does not ferment lactose

8

How and where does Shigella infect?

surface proteins that induce cellular ingestion, uses surface hemolysin to lyse the phagosome membrane and escape into the cytoplasm where it induces actin rocket tails to propel it. First takes up residence in SI then invades colon.

9

Symptoms of Salmonella

can cause bacteremia, enters mesenteric LN and causes classic enteric fever

10

How does Shigella spread?

cell to cell, produces cytotoxic Shiga toxin and induces premature cell death (does not enter the blood stream)

11

Which cause of acute infectious diarrhea is acid resistant?

Shigella

12

How is Shigella transmitted?

fecal oral route (only in humans); children in day cares have high incidence of infection

13

Campylobacter

commoa shaped gram neg rod; paired in a seagull shape. ACID SENSITIVE

14

How and where does Campylobacter infect?

Ingested by monocytes, surviving in the gut for 6-7 days. Once intracellular it induces cell death and tissue necrosis and intense inflammatory reaction which allows it to enter the blood stream.

15

How is Campylobacter transmitted?

It commonly infects poultry (10x more common in chicken than Salmonella)

16

ETEC pathology

enterotoxigenic strains of E. coli. Colonize the small bowel and produce a cholera like or heat stable toxin.

17

ETEC is found

in developing countries: water is contaminated w/ human sewage

18

ETEC diarrhea

stimulates secretion of chloride, causing watery diarrhea

19

ETEC tx

Ciprofloxacin or Levofloxacin

20

Which E coli is a main cause of travelers diarrhea?

EHEC

21

EHEC pathology

produces verotoxins or shiga like cytotoxins that inhibit protein synthesis and cause cell death

22

EHEC is found

in industrialized nations, associated with undercooked beef or unpasturized milk (Cattle is primary resevior)

23

EHEC diarrhea

toxin damages endothelium in the bowel and glomeruli, causing hemorrhagic inflammatory colitis and hemolytic uremic syndrome

24

EHEC Tx

no tx; avoid anti motility drugs (increase toxin release and worsen hemolytic uremic syndrome). Supportive Care ONLY

25

V. Cholera toxin

gains entry to small bowel when host ingests contaminated water or food. (NEUTRALIZED BY STOMACH ACID) Attaches to small intestine and creates cholera toxin. Endotoxin binds to specific receptor in bowel mucosa that activates adenylate cyclase causing an increase in cAMP, elevated cAMP in turn promotes secretion of chloride and water causing voluminous watery diarrhea

26

Rugose

a/w cholera. an aggregation of bacteria surrounded by a protective biofilm, that blocks killing by chlorine and other disinfectants

27

Gastroenteritis

acute diarrhea (lasts less than 14 days), abdominal pain, diffuse pain and tenesmus

28

Clinical manifestations of enteric fever caused by s. typhi and s. paratyphi

COME BACK

29

Watery Diarrhea Etiologies:

ETEC and Vibrio

30

Bloody Diarrhe Etiologies:

Shingella, Campylobacter, EHEC

31

Tx of Shingella

Cipro

32

Tx of Salmonella

Cipro

33

Tx of Campylobacter

Azithro

34

Tx of V. cholera

Cipro

35

Tx of C. diffe

Metronidazole

36

C. Diffe

spore forming, gram negative rod that produces watery diarrhea. Releases 2 toxins (A and B) that bind to and kill cells in the bowel wall. There is a third toxin, binary toxin, that is a/w severe disease.

37

Pathogenesis of C. Diffe

Forms shallow ulcers and pseudomembranes seen on colonoscopy (or CT)

38

C. Diffe is most associated with....

Abx diarrhea, specifically clindamycin

39

How does C. Diffe spread?

Person to person

40

Signs and symptoms of C. Diffe

crampy bilateral lower abdominal pain that is decreased after a BM, low grade fever, mild peripheral leukocytes, TOXIC MEGACOLON, thumbprinting is seen

41

Dx of C Diffe

Cytotoxicity assay, ELIZA can detect toxin A and B

42

What is the most common form of infectious diarrhea

Viral diarrhea

43

What causes viral diarrhea?

The disease is caused primarily by four viral groups: 

Norovirus (“Norwalk”), Rotavirus, Enteric adenovirus 40, 41, Astrovirus. For these etiologies no PMNs found in stool.

44

Norovirus Diarrhea

blunts intestinal villi, causes mild malabsorption, is resistant to chlorine, is spread by contaminated water (including swimming pools), and primarily infects adults

45

Rotavirus Diarrhea

Causes lactase deficiency, and primarily infects infants. Resists hand washing. Peaks in winter

46

Enteric adenovirus diarrhea

Infects infants and young children; peaks in summer months

47

Astrovirus Diarrhea

Infects children in pediatric wards & elderly in nursing homes

48

Tx for viral diarrhea

Self-limiting diseases; use supportive care w/ hydration