Listeria monocytogenes

Listeria monocytogenes is a pathogenic (disease causing) bacterium that is food borne and causes an illness called listeriosis. Listeria survives at temperatures from freezing (0 deg C) to 5 deg C, it will exhibit growth from as low as 4 deg C but like almost all Food poisoning bacteria it grows best between 20 to 40 deg C. As a result listeria may be transmitted in ready to eat foods that have been kept properly refrigerated (2 to 5 deg C). Its ability to grow in such diverse environments is just one of the many challenges presented by this dangerous bacteria.

Listeria monocytogenes is widely distributed in nature, being found in sewage, decaying vegetable matter, all farm animals, domestic pets and man. It is very hardy and is able to grow at low temperatures ie, in a refrigerator.

The presence of the bacteria usually indicates poor personal hygiene practises during manufacture or distribution.

• Wash salad goods before use.
• Never eat cooked chilled products after the "use by" date.
• Ensure food that is reheated attains a centre temperature of at least 70 deg C
• Refrigerator temperature below 5 deg C.

Foods incriminated

Foods known to have caused listeriosis include commercially chilled foods such as prepared salads, sandwiches, pate', cooked meats and ready meals. Other suspected foods are milk, ice cream, raw and smoked fish, soft cheeses.

Target Populations

Certain groups of individuals are at great risk from listeriosis. These are pregnant women (and their unborn children) and immunocompromised persons eg, transplant recipients. Among infants, listeriosis occurs when the infection is transmitted from the mother, either through the placenta or during the birthing process.