Listeria monocytogenes

What is Listeria monocytogenes?

Listeria monocytogenes has been recognized as a human pathogen for 60 years, but food was not thought to be a vehicle of transmission until recently. In the United States, an estimated 2,000 persons become seriously ill with listeriosis each year. Of these, 500 die. Pregnant women, newborns, and adults with weakened immune systems are primarily at risk. About one-third of Listeria monocytogenes cases occur during pregnancy.

Listeria monocytogenes is found in soil and water. Vegetables can become contaminated from the soil or from manure used as fertilizer. Animals can carry the bacteria without appearing ill and can contaminate foods of animal origin such as meats and dairy products. The bacteria can be found in a variety of raw foods, such as uncooked meats and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheeses and cold cuts at the deli counter. Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacteria.

Symptoms vary and depend on the individual's susceptibility, but may include fever, fatigue, nausea, vomiting and diarrhea.

More Information on Listeria monocytogenes:


  • Article History
    • Revision Date: 6/22/2010

Food Safety Tip of the Day

Divide and conquer

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Large amounts of leftovers should be divided into small, shallow pans for quicker cooling. Increasing the exposed surface area of the food will help it cool more rapidly. The goal for proper food cooling is to get the inner-most temperature to less than 70°F within two hours and below 41°F within an additional four hours.

Source: Partnership for Food Safety Education

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