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Microorganisms and foodborne illness

Foodborne illness (or 'food poisoning') is caused by eating food contaminated with harmful microorganisms. Microorganisms are very small organisms you need a microscope to see, including:

What microorganisms cause foodborne illness?

Some microorganisms are more common than others in food. For example:

  • raw chicken and eggs are at higher risk of Salmonella because it often lives in chickens
  • rice and pasta are at higher risk of Bacillus cereus because it lives in soil and can get into grains
  • deli meats and pre-prepared salads are at higher risk of Listeria because it is a common environmental contaminate and can persist in food production environments.

Most of these microorganisms can grow very quickly at warm temperatures between 5°C and 60°C. This is called the 'temperature danger zone'. Food should not be left at these temperatures for more than a few hours.

Some microorganisms can live and grow in different conditions, for example:

  • Listeria can tolerate cold and salty environments and can continue to grow on food even after it has been put in the fridge.
  • Bacillus and Clostridium have spores that can survive cooking, continue to grow and produce toxins if food is cooled too slowly.
  • Botulinum spores can grow where there is very low oxygen (e.g. in vacuum packed or home bottled food).

What's the risk?

These microorganisms can cause gastro or neurological illness, long-term problems such as arthritis and kidney failure, or even death.

Anyone can get foodborne illness but children under 5, pregnant women, people over 65 and people with weak immune systems are at higher risk of becoming seriously ill or dying.

Reduce your risk

Food poisoning microorganisms do not change the smell, taste or appearance of the food. It's important to always handle food in a way that keeps it safe - follow the tips on our Food safety basics page.

More information

Food businesses have systems in place to prevent contamination of food. But even with the best systems, contamination with bacteria or viruses sometimes happens. This is why Australia has a well-established system for recalling food. Food recalls are coordinated by FSANZ in consultation with the food business and the states and territories.

If a food business discovers it has sold unsafe food, it must immediately stop further sales and recall the food. It must let people know, through a notice in a paper or web site, a media release or shop front sign, that the food may be unsafe and should be returned to the seller.

After a recall, a food business will determine what went wrong and put in place new procedures to reduce the chance of it happening again.

Page last updated 6 December 2023