[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/) › Bacillus cereus

[Microbiology](https://durgical.com/en/microbiology/) · [Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/)

# Bacillus cereus

- Bacterium
- Gram-positive
- For completeness

A spore-forming bacterium that causes food poisoning from reheated rice (fast vomiting) or from other foods (diarrhoea).

Updated 2026-11-01

Also called: fried rice syndrome

## Key points

- Reheated rice = emetic form from cereulide.
- The emetic toxin is heat-stable: reheating does not destroy it.
- Vomiting within hours, like S. aureus food poisoning.
- The diarrhoeal form comes later and resembles C. perfringens.

## At a glance

**Gram**
Gram-positive

**Shape**
Large rods

**Oxygen**
Aerobe or facultative anaerobe

**Family**
Bacillaceae

**Stain**
Gram positive; spore former

## Morphology

- Large Gram-positive rods
- Spores that survive cooking
- Motile, unlike B. anthracis

## Transmission

- Cooked rice left at room temperature and briefly reheated
- Poorly chilled meat, vegetables and sauces (diarrhoeal form)

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- Cereulide: heat-stable emetic toxin already formed in the food
- Heat-labile enterotoxin made in the gut (diarrhoeal form)

## Diseases it causes

- Emetic or diarrhoeal food poisoning [Acute (viral) gastroenteritis →](https://durgical.com/en/conditions/acute-gastroenteritis/)
- Endophthalmitis after eye trauma and infections in people who inject drugs

## Clinical picture

- Emetic form: nausea and vomiting a few hours after eating
- Diarrhoeal form: watery diarrhoea and cramps later
- Fever is uncommon

## Diagnosis

- Clinical and epidemiological diagnosis
- In outbreaks: high counts of the bacterium in the implicated food

## Treatment

The food poisoning settles on its own and needs only rehydration. Invasive infections (eye, blood) are treated with antibiotics such as vancomycin, because the bacterium makes beta-lactamases.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Vancomycin](https://durgical.com/en/pharmacology/vancomycin/)

## Prevention

- Chilling rice and cooked foods promptly
- Not keeping food warm for hours
- Reheating thoroughly

## Memory aid

Cereus as in cereal: the rice forgotten in the pot overnight.

## Test yourself

Think of the answer, then tap the question to see it.

## Which food is classically linked to the emetic form of B. cereus?

Cooked rice left at room temperature and then fried or reheated.

## Why does reheating rice not prevent the emetic form?

Because cereulide is heat-stable and already formed in the food.

## Which other food poisoning is confused with the emetic form?

Staphylococcus aureus enterotoxin poisoning, which also causes vomiting within hours.

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## Related

- [Bacillus anthracis](https://durgical.com/en/microbiology/bacillus-anthracis/)
- [Clostridium perfringens](https://durgical.com/en/microbiology/clostridium-perfringens/)

## Related conditions

- [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Bacillus cereus Food Poisoning Associated with Fried Rice at Two Child Day Care Centers -- Virginia, 1993](https://www.cdc.gov/mmwr/preview/mmwrhtml/00025744.htm) (CDC (MMWR), 1994); [Food poisoning: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001652.htm) (MedlinePlus (NLM), 2024).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/bacillus-cereus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/bacillus-cereus/