A bacterium that can grow at refrigeration temperatures and poses a serious risk to pregnant women and other vulnerable people.
A bacterium that can grow at refrigeration temperatures and poses a serious risk to pregnant women and other vulnerable people. Listeria monocytogenes is a bacterium that causes listeriosis. Unlike most food-safety pathogens, it can grow slowly even at normal refrigeration temperatures, which makes it a particular concern in ready-to-eat foods with a long chilled shelf life. It is widespread in the environment and can contaminate foods such as soft cheeses, pre-prepared salads, deli meats, pate, smoked seafood and rockmelon. For most healthy people listeriosis causes mild or no symptoms, but for vulnerable groups it can be severe. Pregnant women are at high risk because infection can cause miscarriage, stillbirth or serious illness in the newborn. Older adults and people with weakened immune systems can develop serious bloodstream or brain infections. The incubation period can be long, sometimes several weeks, which can make outbreaks hard to trace. Food businesses that serve vulnerable people, such as hospitals, aged-care facilities and childcare centres, need to pay special attention to Listeria. Standard 3.2.2A and related guidance emphasise controls for these settings. Practical measures include strict temperature control, short use-by times on high-risk ready-to-eat foods, thorough cleaning and sanitising, and avoiding higher-risk foods for vulnerable consumers. Because Listeria can grow in the fridge, refrigeration slows but does not stop it, so time limits on chilled ready-to-eat foods matter. Businesses should follow date marking carefully, avoid serving listeria-risk foods such as soft serve, pre-cut fruit, cold deli meats and soft cheeses to high-risk groups where guidance advises against it, and keep equipment and cool rooms clean to prevent the bacteria establishing. An aged-care kitchen serves residents a platter of cold sliced ham and soft cheese that has been in the cool room close to its use-by date. Listeria present in the products has had time to grow at fridge temperature, and a resident with a weakened immune system develops a serious infection. Serving freshly opened, lower-risk foods within a short time and observing use-by dates would have reduced the risk.
Frequently asked questions
Why is Listeria different from other food-poisoning bacteria?
Listeria monocytogenes can grow slowly at refrigeration temperatures, so keeping food cold slows but does not stop it. This makes time limits and date marking on chilled ready-to-eat foods especially important.
Who is most at risk from Listeria?
Pregnant women, newborns, older adults and people with weakened immune systems. In pregnancy it can cause miscarriage or stillbirth, so higher-risk foods are best avoided.
Which foods are high risk for Listeria?
Soft and semi-soft cheeses, cold deli meats, pate, pre-prepared or pre-cut salads and fruit, smoked seafood, soft serve and unpasteurised dairy are commonly named higher-risk foods.
How long after exposure do symptoms appear?
The incubation period can be long and variable, sometimes up to several weeks. This delay can make it difficult to link illness back to a particular food.
How should businesses serving vulnerable people manage Listeria?
Follow Standard 3.2.2A where it applies, keep strict temperature control, observe use-by dates, clean and sanitise thoroughly, and avoid higher-risk foods for vulnerable groups in line with health guidance.
