Gastroenteritis Flashcards
Sources of GI infections:
1) Infected food and water
2) Fecal-oral transmission (via contaminated objects)
3) Person-to-person transmission
Most likely illness in recent travelers:
ETEC (enterotoxigenic E. coli)
Most likely illnesses in food-borne infections:
Norovirus Salmonella (NOT typhi) Toxoplasma Listeria Campylobacter
Food-borne infections (1-6 hour incubation):
Staph aureus: mayo, cream pastry, ham, poultry
Bacillus cereus: fried rice
Food-borne infections (8-14 hour incubation):
Clostridium perfringens: beef, poultry, legumes, gravy
Bacillus cereus: meat, vegetables, dried beans, cereals
Food-borne infections (>16 hour incubation):
Vibrio cholera: shellfish
Vibrio parahemolyticus: oysters, shellfish
ETEC: salad, cheese, meat, water
Salmonella: beef, poultry, eggs, dairy
Shigella: potato or egg salad, lettuce, raw vegetables
Most likely illness following antibiotic treatment:
Clostridium difficile
Most likely illness following sexual contact:
Shigella (among MSM). Hepatitis A.
Most likely illness from pets:
Salmonella from reptiles and amphibians. Recent turtle outbreaks of S. enterica.
Most likely in the immunodeficient:
Cryptosporidium, microsporidium, cyclospora, isospora.
Most likely in pregnant women:
Listeria, hepatitis E
Most likely in the young:
Rotavirus, norovirus
Causes of non-inflammatory (enterotoxic) diarrhea:
Vibrio cholerae Clostridium perfringens Bacillus cereus ETEC Rotavirus Giardia Cryptosporidium
Causes of inflammatory (invasion or cytotoxic) diarrhea:
Shigella Salmonella (not Typhi) Campylobacter EHEC EIEC Yersinia enterocolitica Vibrio parahemolyticus Clostridium difficile Entamoeba histolytica
Causes of penetrating diarrhea:
Salmonella typhi
Yersinia enterocolitica
Diarrhea:
Acute (0-14 days)
Persistent (>14 days)
Chronic (>30 days)
Although gastroenteritis is typically self-limited, the following scenarios require further work-up:
Bloody diarrhea
Profuse diarrhea with evidence of hypovolemia
Small volume stools with blood and mucus
Hospitalized, immunocompromised, and pregnant patients
Fever or other evidence of systemic disease
Duration of symptoms >48 hours, or >6 stools in 24 hours
Diarrhea in the setting of recent antibiotic exposure.
Testing in gastroenteritis:
Fecal WBC
Lactoferrin
Stool culture (salmonella, shigella, campylobacter, EHEC)
Ova and parasites (giardia, cryptosporidium, Entamoeba histolytica)
C. diff toxin antigen
Treatment:
Generally not required.
Rehydration is critical.
Some organisms (EHEC) worsen with antibiotic therapy.
Non-infectious causes of diarrhea:
Inflammatory bowel disease GI tumor Endocrine disease (carcinoid) Secretory diarrhea (laxatives) Medication associated diarrhea (NSAIDs, colchicine, metoclopramide) GI bleeding IBS Ischemic colitis Radiation colitis Necrotizing enterocolitis Bowel prep for colonoscopy
Norovirus:
Damages brush border, preventing uptake of water and nutrients. Associated with outbreaks. Presents with acute onset of vomiting, mild fever, abdominal cramps, non-bloody diarrhea. Duration 1-2 days.
Diagnosis via PCR.
Rotavirus:
Main cause of pediatric diarrhea. 2 day incubation. Vomiting and watery diarrhea for 3-8 days, can be associated with fever and abdominal pain.
Diagnosis via rapid antigen detection.
Shigella (S dysenteriae, flexneri, sonnei):
Invades colonic epithelia, causing superficial ulceration and colitis with abscesses, impaired absorption of water and electrolytes.
Fecal-oral transmission. Predilection for children, daycare, poor sanitation, and MSM.
Causes dysentery with fever and blood flecks in stool. Children can develop HUS due to Shiga toxin.
Diagnosis via stool culture.
Treatment: AMPICILLIN (TMP/SMX or CIPRO for resistant strains). Avoid anti-motility agents.
Salmonella typhi (typhoid fever):
Organisms penetrate mucosa, are carried to lymph nodes and blood with secondary excretion into intestine from bile. Humans may serve as reservoirs. NO ANIMAL RESERVOIR. Presents with malaise, myalgias, headache, and high fever. ROSE SPOTS and TEMPERATURE-PULSE DISSOCIATION are common. Intestinal perforation is possible. Blood culture positive early, stool culture positive later.
Treatment: ampicillin, TMP/SMX, ciprofloxacin
Prevention: live oral vaccine
Other salmonella (S enteritidis, typhimurium)
Pili adhere to small intestine where enterotoxin stimulates fluid secretion. Numerous animal reservoirs (poultry, eggs).
Presents as gastroenteritis with sudden onset of nausea, crampy abdominal pain, diarrhea and fever.
Diagnosis via stool culture.
Treatment: only for severe disease, immune compromise or extremes of age (TMP/SMX or ciprofloxacin)
Campylobacter jejuni
Inflammatory diarrhea of the ileum and colon. Many animal reservoirs, transmission in poultry, unpasteurized milk, and water.
Presents with headache, myalgias, fever, and acute non-bloody diarrhea.
Diagnosis via stool culture
EPEC:
Adheres to and destroyes microvilli. Important cause of childhood diarrhea in developing countries.
ETEC:
Milder, cholera-like watery diarrhea from production of enterotoxin (LT or ST). Causes TRAVELER’S DIARRHEA.
EIEC:
Causes inflammatory diarrhea.
EHEC:
Cytotoxin causes bloody diarrhea, may be complicated by HUS.
Clostridium difficile:
Toxin causes diarrhea and pseudomembranous colitis.
Treatment is oral metronidazole (or vancomycin for severe illness).
Yersinia enterocolitica:
Mucosal ulcerations and MESENTERIC ADENITIS. Intracellular pathogen. There is an animal reservoir with outbreaks from food and water. Presents with appendicitis-like illness.
Treatment: tetracycline and TMP/SMX.
Vibrio parahemolyticus:
Mild tissue damage and watery diarrhea (invasion and toxin production). Inadequately cooked seafood. Explosive watery diarrhea with low grade fever. Diagnosis via stool culture.
Vibrio cholera:
Non-inflammatory toxin acts on small bowel. Adenylate cyclase stimulation leads to increased cAMP and massive fluid loss. Food and waterborne. Causes RICE-WATER STOOLS.
Diagnosis: Stool culture
Treatment: ORT. Tetracycline.
Listeria monocytogenes:
Intracellular pathogen, passes through intestines into macrophages and causes disseminated infection. Coleslaw, dairy products, cold processed meats. Causes fever, myalgias, bacteremia, and meningitis.
Diagnosis via blood or CSF cultures.
Treatment: Ampicillin
GI bugs that should be treated:
1) Shigella (usually ampicillin, sometimes TMP/SMX)
2) Salmonella (not Typhi) - only if severe (TMP/SMX or ciprofloxacin)
3) Clostridium difficile (metronidazole OR vancomycin for severe illness)
4) Yersinia enterocolitica (tetracycline or TMP/SMX)
5) Vibrio cholera (tetracycline)
6) Listeria monocytogenes (ampicillin)
Fever or severe abdominal pain suggests:
Invasive disease
Vomiting suggests:
Toxin-mediated disease
Abdominal bloating suggests:
Giardia (outdoor exposure)
Dizziness suggests:
Severe dehydration or chronicity
Tenesmus suggests:
Rectal inflammation (consider shigella, other STDs)
Consider antibiotics (fluoroquinolones or azithromycin) if:
Diarrhea is severe (>8 episodes/day) or prolonged (>7 days).
Once major infections have been ruled out, one can use:
Loperamide
