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Bacillus cereus in food

Bacillus cereus. Source: Mogana Das Murtey and Patchamuthu RamasamyLast updated: 22 December 2020

What is it?

  • Bacillus cereus (B. cereus) is a type of bacteria widespread in the environment
  • It can form spores and toxins that are not destroyed by cooking or boiling
  • Foods at higher risk of contamination include pre-cooked starchy foods like rice, pasta and cereals, and pre-cooked mixed dishes, especially spiced dishes

What's the risk?

  • B. cereus can cause vomiting and diarrhoea
  • Anyone can get sick with B. cereus but vulnerable people (i.e. young children, pregnant women, the elderly) and people with weak immune systems (like cancer patients) can get seriously ill

What illness does it cause?

There are two types of illness: emetic (vomiting) and diarrhoeal.

Neither of these illnesses are nationally notifiable (they don't need to be reported to health authorities unless there is an outbreak—linked illness in two or more people).

Reduce your risk

  • Cook food thoroughly and serve it immediately or keep it hot (60oC or hotter) before serving
  • Cool cooked food quickly if it is going to be used later:
    • put it in the fridge (or freezer) as soon as it stops steaming
    • divide large amounts of hot food into smaller containers to let it cool faster
    • make sure your fridge is 5oC or colder
  • Keep leftovers in the fridge (or freezer) and dispose of refrigerated leftovers if not eaten within 3-4 days (or within 1 day for vulnerable people
  • Wash your hands with soap and dry them before preparing and eating food
  • Keep your kitchen and equipment clean

Symptoms of illness from B. cereus

  • Symptoms usually start 1 to 16 hours after eating contaminated food. Common symptoms are nausea, vomiting, abdominal cramps, and watery diarrhoea
  • Most people only have mild symptoms and recover quickly (within a day or less)

Image credit: Mogana Das Murtey and Patchamuthu Ramasamy


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