Getting To Know Listeria

Save PDF

Most people know about Salmonella, E. coli and Botulism and are now, unfortunately, adding Listeria to their list of frequently heard of foodborne illnesses.

Listeria monocytogenes (L. monocytogenes) is not one of the top most frequently occurring foodborne illnesses, but it is one of the most costly and deadly. Listeria—the illness is called listeriosis– causes the third highest number of foodborne illness related deaths in the United States annually. The Center for Disease Control and Prevention (CDC) estimates 1,600 people get listeriosis each year, and about 260 die.

What makes Listeria scary is that it resists some of the things—salt, nitrates and acidity– that are usually used to control bacteria growth. What makes it extra scary is that Listeria can grow and live for a long time at refrigerator temperatures. These pathogens can easily hide in nooks and crannies of a refrigerator, cooler or manufacturing equipment for a long time. You can’t see, taste or smell Listeria in foods.

A good thing about Listeria is that it takes a large amount to make someone sick and most healthy people will not get sick from eating foods contaminated with Listeria. The people that are at the highest risk to get listeriosis are pregnant women because it could lead to miscarriage, stillbirth or septicemia or meningitis in the newborn. Others at risk are people with organ transplants, children, the elderly and those that are immune suppressed due to illnesses such as cancer, renal disease, diabetes and AIDS.

The good news is that proper cooking and reheating of foods can control Listeria. The bad news is many of the items that have been found to contain Listeria are foods that we don’t usually eat cooked. The most risky foods are those that are kept in the refrigerator for a long time (cheeses), cooked foods that have been further handled (lunchmeats, hot dogs, and meat spreads) and foods that are minimally processed (fresh fruits, vegetables and cold smoked seafood). In the past couple of years Listeria has been found in hummus, ready-made salmon salad, sliced cooked chicken, leafy greens, sprouts, fresh cut vegetables, ice cream, unpasteurized cheese, frozen produce, caramel apples, cantaloupe and even cat food.

What can you do to protect yourself from Listeria?

• Keep perishable foods refrigerated
• Prevent ready-to-eat foods from being cross contaminated by raw foods.
• Cook beef, pork and poultry to the recommended minimum internal temperatures.
• Wash raw fruits and vegetables before eating.
• Avoid unpasteurized milk or foods made from raw milk.
• Read and heed label instructions to “keep refrigerated” and “use by” dates on refrigerated foods.
• Only keep leftovers three to four days. Heat leftovers and “ready to eat foods” to at least 165 degrees F.
• Those especially at risk should avoid soft cheeses such as Feta, Brie and blue-veined cheeses, as well as unheated lunchmeats, hot dogs and frozen vegetables.
• Pay attention to food recalls.

Keep your refrigerator clean and as cold as possible (40 degrees or lower). Although Listeria can grow in the refrigerator, it grows more slowly under colder conditions. Use a refrigerator thermometer to double-check the temperature is below 40 degrees F. Clean and sanitize the shelves of your refrigerator regularly.

References:
Listeria, FSE 99-21, Pat A. Curtis, Ph.D and John E. Rushing, Ph.D, Department of Food Science, North Carolina State University. https://fbns.ncsu.edu/extension_program/documents/foodsafety_listeria.pdf
Barfblog, Benjamin Chapman, Ph.D, State Specialist, NCSU and Doug Powell, Ph.D, Barfblog publisher. www.barfblog.com
Listeria (Listeriosis) The Center for Disease Control and Prevention, https://www.cdc.gov/listeria/index.html