Listeria has been mentioned in quite of few of my articles as a potential cause of food-borne illnesses. But what exactly is listeria and how is it introduced into food? Here are a few interesting facts which can help you to become more aware of this bacteria and how to reduce the likelihood of being infected by it.

What is listeria?

Listeria monocytogenes is bacteria that is found in soil and water; it can also be found in livestock that is consumed, such as poultry and cattle. It can survive in temperatures from 4 °C (the temperature of a refrigerator) up to 42 °C. Listeria is the third most deadly food-borne illness and is known for its high fatality rate when compared to others. According to the Centers for Disease Control in the United States, an estimated 1,600 people get listeriosis each year from consuming contaminated food, with a death rate of 260. The bacteria has an incubation period of 3-70 days which means you may not experience symptoms immediately after consuming.

What are the potential sources?

Given that listeria can be found in soil, water and livestock there are numerous points at which it can be introduced to food. Some of these include unpasteurised raw milk and dairy products, soft cheese made with unpasteurised milk such as feta and brie, raw sprouts, ready-to-eat deli meats and hot dogs, lettuce, meat spreads. This bacteria can also be found in food processing plants, on food contact surfaces and on floors. Additionally, listeria can also grow and spread in your refrigerator and other storage areas. Which means that cross-contamination can occur with other foods during storage.

What are the symptoms and long-term effects?

The symptoms of a mild listeria infection may pass within a few days without treatment, with symptoms such as fever, stiff neck, confusion, weakness, vomiting, sometimes preceded by diarrhoea. However, if the bacteria infects your bloodstream it can become a problem, resulting in meningitis, septicemia, abortion, and even death. The Centers for Disease Control has reported that up to 20 per cent of people with listeriosis die.

Who is at risk?

Of course, everyone who consumes contaminated food is at risk of being infected. However, the following high-risk groups need to be mindful of what they consume, and how: children under the age of six, older adults, pregnant women, people with weakened immune systems such as those with cancer, HIV/AIDS, liver disease, and diabetes.

How can you prevent contamination and cross-contamination?

Listeria can spread from one surface to another and can be transported from one area to the next on contaminated produce, equipment or clothing. You can do the following to minimise or eliminate the risk of being infected:

– Ensure proper cleaning and sanitation of all floors and do not store food or food containers on the floor.

– Avoid drinking raw (unpasteurised) milk, and eating foods that have unpasteurised milk in them.

– Always wash and sanitise hands before handling food and ensure knives, countertops, and cutting boards after handling and preparing uncooked foods are cleaned with warm soapy water and sanitised.

– Clean refrigerators frequently. Ensure all spills — especially those from raw meats — are cleaned with warm water and soap. If a cloth is used to clean the area, ensure this is kept clean at all times, to prevent cross-contamination with other surfaces.

– Raw produce must be washed thoroughly under running tap water before eating. Additionally, you may want to try to sanitise by creating your own sanitiser using 1 tsp of unscented bleach to one quart of water and letting it stand for 10 minutes before using.

– Separate uncooked meats, poultry and seafood from vegetables, fruits, cooked foods, and ready-to-eat foods: put the latter on the top shelves and the others below.

– Ensure raw foods from animal sources are cooked to the required internal temperatures.

– Individuals mentioned above as high-risk groups must ensure they heat hot dogs, cold cuts, and deli meats before eating them, along with paying close attention to the other preventative measures.

– Keep all refrigerated foods cold; while listeria can grow at refrigeration temperatures, it grows more slowly at refrigerator temperatures of 40 degrees F/4 degrees C or less and the freezer at 0 degrees F/-17 degrees C or lower.

– Ensure all foods placed in refrigerator are covered and that there is no leakage in containers.