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Microorganisms and foodborne illness

​Last updated 1 March 2021

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 microorganism​​​s 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. 


  • Wash your hands thoroughly with soap and dry them before preparing and eating food
  • Keep your kitchen equipment and utensils clean.


  • Cook food thoroughly
  • Serve it immediately or keep it hot (60°C or hotter) before serving
  • Reheat chilled food quickly with a microwave or stovetop until it's piping hot (75°C) all the way through.


  • Cool cooked food quickly if it is going to be eaten later
  • Keep cold food cold (check your fridge is 5°C or colder and your freezer is -20°C or colder)
  • Eat leftovers within 3-4 days (or within 1 day for vulnerable people).


  • Keep raw food (especially meats) separate from foods that are ready to eat
  • Use different cutting boards for raw meat and salad (or other ready to eat foods)
  • Store raw meats in the fridge below foods that are ready to eat.


  • Avoid higher risk foods if you or your family are vulnerable. Examples are raw and lightly cooked eggs, undercooked meat products and raw seafood
  • Do not eat food that has passed its use by date.

More information:

For more information on the different microorganisms found in food see:

​Did you know?

Food businesses have systems in place to prevent contaminati​on 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 Miand 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. ​

More information:

Food recall system


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