Infectious Disease Compendium

Gastroenteritis

Diagnosis

Nausea/vomiting with or without diarrhea, with or without cramps.

Epidemiologic Risks

Often you are what you eat. You can eat a bug or a preformed toxin, the it makes you vomit like Vesuvius or crap like, well, is there a volcano that starts with c? I like alliteration.

Microbiology

Viral causes: CMV, Noro Virus causes13% of all gastroenteritis-associated ambulatory visits, with ∼50% of such visits occurring during November–February (PubMed).

Bacillary Causes: Aeromonas, Bacillus, E. coli, Campylobacter, Klebsiella oxytoca, Listeria monocytogenes (your lab will not be looking for it), Plesiomonas, Salmonella, S. aureus (it may well cause disease, esp MRSA), Shigella, Vibrio, Yersinia.

Toxin mediated: B. cereus (long incubation), B. cereus (short incubation), Clostridium botulinum, Clostridia difficile, Clostridium perfringens, S. aureus.

Parasites: Cyclosporidia, Cryptosporidia, Entamoeba histolytica, Giardia, Isospora.

Eosinophilic: Ancylostoma caninum, A. costaricensis, Anisakis.

Empiric Therapy

Mostly supportive. Depends on which of the above organisms you are concerned about. Most will get better on their own and do not need treatment. For bacillary diarrhea, usually a quinolone OR rifaximin except for Campylobacter jejuni. Treatment of Escherichia coli may make HUS more likely BUT treatment of E. coli associated travelers diarrhea may lead to less irritable bowel syndrome.

Pearls

People blame the most recent meal, but with the exception of staphylococcal and bacillus toxins, to get nausea and vomiting takes more than 6 hours.

C. perfringens is the cause of 10% of outbreaks and is mistaken for norovirus (PubMed).

Rants

ICD9 Codes (Soon to be supplanted by ICD10)

Gastroenteritis 558.9; salmonella 003.0; viral NEC 008.8 specified type NEC 008.69.