Listeria

This page provides information about the risks associated with Listeria and provides advice in relation to food with a high risk of Listeria contamination.

What is Listeria?

Listeria monocytogenes is a type of bacteria that can cause a serious illness called listeriosis in some people. The major cause of Listeria infection is through the consumption of contaminated food. Listeria is widespread in nature and is commonly found in soil, water, mud, vegetation and sewerage. It can also be found in raw meat, raw vegetables and unpasteurised dairy products. Some exposure to these bacteria is unavoidable. Every day, most healthy people eat foods that contain small amounts of Listeria with no apparent ill effects.

Who is at risk?

Listeriosis is uncommon in healthy people, however, it can be extremely serious or even life-threatening for people at high risk including:

• older people (people over 65 years)
• pregnant women, their unborn and newborn children
• people with weakened immune systems (e.g. cancer, AIDS, diabetes, liver or kidney disease)
• anyone on medication that can suppress the immune system (e.g. prednisone or cortisone).

What are the symptoms of listeriosis?

Listeriosis is a rare disease and if infected, healthy people, including pregnant women, experience few or no symptoms. If symptoms are present, they may vary from:

• minor complaints such as:
  • fever
  • headache
  • aches and pains
  • vomiting and
  • diarrhoea
• to more serious forms of the illness such as:
  • meningitis (infection of the lining of the brain)
  • septicaemia (blood poisoning)
  • infection during pregnancy may lead to miscarriage, stillbirth, premature birth or a very ill newborn. The death rate in infected newborn babies is 20-30%.

The average time from exposure to the development of symptoms of the disease is about 3 weeks.

What foods have a high risk of Listeria contamination?

High risk foods are usually chilled ready-to-eat foods including:

• pate or meat spreads
• soft cheeses (e.g. brie, camembert, blue, feta and ricotta)
• cooked ready-to-eat chicken (e.g. as used in sandwiches, whole, portions or diced)
• cold meat products from delicatessens or sandwich bars or packaged and sliced, ready-to-eat (e.g. cold roast meat, processed meats such as ham and salami)
• pre-prepared fruit and vegetable salads (e.g. packaged salads from supermarkets, buffets and salad bars)
• smoothies and salads made from packaged frozen vegetables
• rockmelon
• raw or smoked seafood and chilled seafood (e.g. oysters, sashimi, sushi and prawns)
• soft serve ice cream
• unpasteurised dairy products.

What foods are considered safe?

Foods that are generally considered to be safe from Listeria contamination include:

• freshly cooked foods
• hard cheeses
• fresh pasteurised milk and milk products
• UHT milk
• yoghurt
• fresh, washed fruit and vegetables purchased whole
• canned foods.

How can food be prepared safely for vulnerable people?

• Conventional cooking destroys Listeria. Freshly cooked food is the safest. Hot food should be thoroughly cooked and kept above 60°C.
• Reheat food until it is steaming hot.
• Refrigerate leftovers promptly and use them within 12 hours, or freeze them. Refrigeration does not stop the growth of Listeria, it is one of the few bacteria that can grow in refrigerated foods.
• Raw fruits and vegetables should be thoroughly washed before eating.
• Uncooked meats should be kept covered and separate from cooked food and ready-to-eat food.
• Knives and cutting boards used to prepare uncooked foods should not be used to prepare cooked or ready-to-eat food.
• Eat foods taken out of cold storage within four hours.
• Always maintain good food and personal hygiene practices when preparing or handling food.

More information

• Queensland Health: Health conditions directory
• For health advice:
  • contact your local doctor or nearest public health clinic
  • call 13 HEALTH (13 43 25 84)