Gastroenteritis

Question 1

Diarrhea v Dysentery

Answer 1

• Diarrhea - most common consequence of gastroenteritis; usually caused by enterotoxins and small intestine damage; frequent, watery d/c
• Dysentery - frequent low volume stools w/ blood and pus; usually caused by inflammation and colon damage

Question 2

Tx of Infectious Diarrhea

Answer 2

• REHYDRATE (restore water and electrolytes)
  
  • Mild - pedialyte or water w/ saltine crackers
  • Moderate - oral rehydration (with Na and glucose to drag water into cells)
  • Severe - IV fluids
• If non-inflammatory then can give anti-motility (loperamide or diphenoxalate - atropine)
• If inflammatory (blood, pus, leuks in feces) then no anti-motility (prolongs contact) but give abx (unless EHEC)
  
  • Quinolones

**traveler should pack a thermometer, loperamide (anti-motility) and broad-spectrum abx; so if sick they can take temp (if no fever just use loperamide; if fever use abx)

Question 3

Viral Gastroenteritis + Example

Answer 3

• In General: brief incubation, vomiting anf diarrhea, esp in infants and young kids
• Ex) Rotavirus
  • ds RNA reovirus
  • More common in winter and in young kids/elderly
  • Kills intestinal cells –> malabsorption
  • No vaccine

Question 4

Vibrio Cholera

Answer 4

• Gram neg rod; oxidase-pos
• Usually spreads in fecally-contaminated water
• Cholera enterotoxin –> inc cAMP –> Cl- secretion –> water diarrhea and severe dehydration
• Tx - fluids and abx

Question 5

Norovirus

Answer 5

• ss RNA (calcivirus)
• Easily spread fecal-orally
• Sudden onset b/c .5-2 day incubation and only lasts 1-2 days
• Damage to intestinal mucosa –> malabsorption
• Tx - fluids and electrolytes (+ prevention via handwashing and disinfecting w/ bleach)

Question 6

Food Poisoning Categorization

Answer 6

• Intoxications (just need to ingest toxin- FAST ONSET)
• Infections (must ingest actual viable pathogen)

1- In Vivo Toxin Production (C. perfringens, B. cereus, EHEC) - MODERATE ONSET; only symptomatic tx

2- Invasion (Salmonella, Shigella, Campylobacter) - SLOW ONSET; see fecal leuks and fevers; treat w/ abx

Question 7

2 Examples of Intoxications

Answer 7

• Ex) Clostridium botulinum
  - Produces neurotoxin –> flaccid paralysis
• Ex) Staph or Bacillus cereus
  - Both produce heat-stable enterotoxins –> vomiting and diarrhea w/in 6 hrs

Question 8

EHEC

Answer 8

• Gram neg rod
• Includes O157:H7 strain (can cause HUS)
• Usually from contaminated foods (or petting zoo)
• Produces Shiga toxin –> kills cells by inhibiting protein synthesis
• Hemorrhagic colitis - bloody diarrhea 4 days after exposure that lasts about 1 wk
• HUS - Shiga toxin absorbed –> circulation –> kidney –> acute renal fail
• Use dialysis or fluids but not abx

Question 9

Salmonella

Answer 9

• Gram neg rod
• 2 types - non-typhoid (#1 US food poisoning) and S. typhi (causes typhoid fever in developing countries)
• Invade thru M cells of Peyers patches
• Non-typhoid stays in intestine and causes nausea, vomiting, cramps, diiarrhea
• S typhi can survive in macrophages then spread via reticuloendothelial tissue (esp to liver) –> multi-organ disease and fever
• Traveler’s vaccine for S. typhi
• Tx - may use abx for non-typhoid and definitely use abx for S. typhi; restore fluids and electrolytes

Question 10

C Diff

Answer 10

• Gram pos, anaerobic, spore-forming rod
• Range from mild abx-associated diarrhea to pseudomembranous colitis (systemic, fever, severe dehydration)
• 1-3% develop megacolon
• Toxins A and B - inflammation and damage colon mucosa
• Dx - toxins A and B in stool
• Tx - fluids, metro/oral vancomycin, fecal transplant (more effective than abx)
• Gloves, handwashing (NOT ALCOHOL), 10% bleach wipes

Question 11

ETEC

Answer 11

Enterotoxigenic E Coli (most common traveler’s diarrhea)

• Gram neg rod
• Fecal-oral transmission
• Causes watery diarrhea w/o fever
• Enterotoxins
  - Heat-labile –> inc cAMP
  - Heat-stable –> inc cGMP
• Treat w/ fluids and electrolytes; can treat symptoms w/ loperamide

Question 12

Gastroenteritis in Immune-Comp

Answer 12

• In General: can be infected w/ normal GI pathogens at lower doses (Shigella, Salmonella)
• OR opportunistic infections
  • In Transplant Pt … CMV, Epstein Barr
  • In HIV/AIDS Pt … entamoeba histolytica, crypto, Giardia, Isospora (parasite), mycobacterium avium intracellulare, CMV, HSV

Question 13

Cryptosporidium Parvum

Answer 13

• Parasite that forms resistant cysts
• Contaminated drinking water
• Dx - modified acid fast stain of stool for cysts
• No effective abx