GI Infections

Question 1

Most common bacterial causes of acute diarrhea

Answer 1

salmonella, shingella, campylobacter, E. coli

Question 2

Salmonella risk factors

Answer 2

antacid use, prior abx use, depressed immune function

Question 3

How do we get Salmonella

Answer 3

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

Question 4

Dx of Salmonella

Answer 4

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

Question 5

Salmonella

Answer 5

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

Question 6

How and where does Salmonella infect?

Answer 6

attach to epithelial cells in SI and colon

Question 7

Shingella

Answer 7

gram neg bacillus, nonmotile, does not ferment lactose

Question 8

How and where does Shigella infect?

Answer 8

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.

Question 9

Symptoms of Salmonella

Answer 9

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

Question 10

How does Shigella spread?

Answer 10

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

Question 11

Which cause of acute infectious diarrhea is acid resistant?

Answer 11

Shigella

Question 12

How is Shigella transmitted?

Answer 12

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

Question 13

Campylobacter

Answer 13

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

Question 14

How and where does Campylobacter infect?

Answer 14

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.

Question 15

How is Campylobacter transmitted?

Answer 15

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

Question 16

ETEC pathology

Answer 16

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

Question 17

ETEC is found

Answer 17

in developing countries: water is contaminated w/ human sewage

Question 18

ETEC diarrhea

Answer 18

stimulates secretion of chloride, causing watery diarrhea

Question 19

ETEC tx

Answer 19

Ciprofloxacin or Levofloxacin

Question 20

Which E coli is a main cause of travelers diarrhea?

Answer 20

EHEC

Question 21

EHEC pathology

Answer 21

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

Question 22

EHEC is found

Answer 22

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

Question 23

EHEC diarrhea

Answer 23

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

Question 24

EHEC Tx

Answer 24

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

Question 25

V. Cholera toxin

Answer 25

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

Question 26

Rugose

Answer 26

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

Question 27

Gastroenteritis

Answer 27

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

Question 28

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

Answer 28

COME BACK

Question 29

Watery Diarrhea Etiologies:

Answer 29

ETEC and Vibrio

Question 30

Bloody Diarrhe Etiologies:

Answer 30

Shingella, Campylobacter, EHEC

Question 31

Tx of Shingella

Answer 31

Cipro

Question 32

Tx of Salmonella

Answer 32

Cipro

Question 33

Tx of Campylobacter

Answer 33

Azithro

Question 34

Tx of V. cholera

Answer 34

Cipro

Question 35

Tx of C. diffe

Answer 35

Metronidazole

Question 36

C. Diffe

Answer 36

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.

Question 37

Pathogenesis of C. Diffe

Answer 37

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

Question 38

C. Diffe is most associated with....

Answer 38

Abx diarrhea, specifically clindamycin

Question 39

How does C. Diffe spread?

Answer 39

Person to person

Question 40

Signs and symptoms of C. Diffe

Answer 40

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

Question 41

Dx of C Diffe

Answer 41

Cytotoxicity assay, ELIZA can detect toxin A and B

Question 42

What is the most common form of infectious diarrhea

Answer 42

Viral diarrhea

Question 43

What causes viral diarrhea?

Answer 43

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.

Question 44

Norovirus Diarrhea

Answer 44

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

Question 45

Rotavirus Diarrhea

Answer 45

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

Question 46

Enteric adenovirus diarrhea

Answer 46

Infects infants and young children; peaks in summer months

Question 47

Astrovirus Diarrhea

Answer 47

Infects children in pediatric wards & elderly in nursing homes

Question 48

Tx for viral diarrhea

Answer 48

Self-limiting diseases; use supportive care w/ hydration