Bacillus cereus

Snapshot

A 25-year-old medical student goes to an urgent care clinic for vomiting and nonbloody diarrhea. He is on a tight budget and has recently been relying on buying bulk amounts of rice and making fried rice. He makes a batch every Monday, and reheats it throughout the week. He finished off his last batch for lunch around 3 hours ago and admits that he had accidentally left that portion out overnight. He reports feeling nauseous. On physical exam, he is afebrile, has hyperactive bowel sounds, and abdominal tenderness. His physician reassures him that this disease is likely self-limited and suggests that he vary his diet.

Introduction

Classification
- Bacillus cereus
  - an aerobic, gram + rod
  - spore-forming and enterotoxin-producing bacteria
- transmission
  - ingestion of spores or toxin
Epidemiology
- risk factors
  - ingestion of (fried) rice or pasta
  - poor practices of handling and storing food
Pathogenesis
- spores are heat resistant and thus can survive cooking rice
  - especially seen with reheated rice, as spores germinate and produces enterotoxin
- produces “emetic toxin” cereulide
  - causes emetic type
Associated conditions
- emetic type
  - associated with reheated rice and pasta
  - within 1-5 hours after exposure
- diarrheal type
  - associated with meats and sauces
  - within 8-18 hours after exposure
Prognosis
- both types starts and ends quickly
- the acute diarrhea is typically self-limited

Presentation

Studies

Differential

Giardiasis
- distinguishing factors
  - patients often report bloating and foul-smelling fatty watery diarrhea and have a history of swimming in or drinking river/lake water
  - typically patients do not vomit

Treatment

Management approach
- as the disease is usually self-limited, antibiotics are generally not necessary
Conservative
- rehydration
  - indication
    - all patients
Medical
- antibiotics
  - indication
    - severe diarrhea
  - drugs
    - clindamycin
    - aminoglycosides

Complications