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Foodborne Illness and Listeria monocytogenes

Posted: September 6, 2016

The past few months has seen numerous recalls of food contaminated with the bacteria Listeria monocytogenes. This particular bacteria grows under refrigeration and is particularly harmful to pregnant women, newborns, children, elderly, and immune compromised individuals.
USDA on flickr.com CC by 2.0

USDA on flickr.com CC by 2.0

When it comes to foodborne illness (food poisoning), most people are familiar with E. coli or Salmonella but less so with Listeriosis. This illness is caused by the bacteria Listeria monocytogenes which is found in the soil, water, decaying vegetation and the intestinal tract of poultry and cattle. It can also be found in the environment of food processing plants and in the retail setting.

Unlike other bacteria, which do not grow under refrigeration, L. monocytogenes will grow at refrigeration temperatures, 38°F to 40°F, and will start to grow more rapidly above 40°F.

Listeriosis is of particular concern for the elderly, pregnant women, newborns, people with weakened immune systems, individuals with liver or kidney disease, diabetes or alcoholism. It is estimated about 1,600 people develop this illness each year with approximately 260 deaths, 90% being from the above mentioned groups.

Symptoms may appear in a few days to several weeks after consuming a food contaminated with this bacteria and generally start as fever, muscle aches, vomiting, nausea and/or diarrhea. However, the symptoms can quickly go beyond the gastrointestinal tract, especially in the high risk groups, and include fatigue, headache, stiff neck, confusion, loss of balance and possibly convulsions. In pregnant women, if the illness if not detected and treated it can cause miscarriage or stillbirth.

Outbreaks of this illness have been traced back to raw milk and milk products, bagged salad mixes and cantaloupes. Most recently, there have been numerous food recalls of frozen vegetables related to contamination with L. monocytogenes. During the past few months, the Food and Drug Administration (FDA) recalled approximately 456 different products containing frozen vegetables from CRF Frozen Foods and other manufacturers that used these vegetables as food ingredients. While the investigation is now closed, consumers may still have product on hand and should be checking labels before use.

Foods commonly associated with this illness include, uncooked meats and vegetables, unpasteurized (raw) milk and cheeses including soft cheeses made with unpasteurized milk such as queso fresco, ready-to-eat deli meats and hot dogs (unless properly cooked), refrigerated pâtés or meat spreads and smoked seafood and raw sprouts. Individuals at higher risk for developing Listeriosis are advised to avoid eating these foods. The bacteria is easily destroyed by cooking foods to the proper temperatures.

The good news is you can do many things to reduce the risk for developing this foodborne illness. The key food safety messages of Fight BAC – Clean, Separate, Cook and Chill - are an important starting point. The FDA, Centers for Disease Control and Prevention and U.S. Department of Agriculture have focused on some additional steps to further reduce Listeria risk. These include:

  • Keep your refrigerator at 40°F or lower and use a refrigerator thermometer to be sure it is at this temperature. Purchase a refrigerator thermometer at your local department store and place it in the middle of your refrigerator for 5 to 8 hours. Check the temperature at that point and if it is not reading between 38°F - 40°F then lower the setting. After that, place the thermometer near the door and monitor the temperature every day to be sure the unit is staying within the desired range.
  • Use ready-to-eat refrigerated foods as quickly as possible. The longer these foods stay in the refrigerator the more time for listeria to grow. Do not keep these items past the use-by-date. For hot dogs store opened packages no longer than 1 week and unopened packages no longer than 2 weeks. Store open packages of lunch/deli meat or meat sliced at the deli counter no longer than 3-5 days. For factory sealed, unopened packages no longer than 2 weeks. If you are in a high risk group be sure to thoroughly heat lunch/deli meats and hot dogs before eating.
  • Clean your refrigerator regularly with hot soapy water, rinse and dry with a paper towel. Be sure to clean up spills as they occur to prevent juices from meats and hot dogs especially from coming in contact with other foods.
  • Wash hands, knives, countertops and cutting boards before and after handling and preparing uncooked foods. If cutting melons, scrub the surface of the melon with a clean and sanitized produce brush under running water and dry with a paper towel before slicing. Once cut keep the melon refrigerated and eat within 7 days.

Hopefully you will never have a foodborne illness, and while the risk may not be great, it only takes one misstep for a problem to occur. So follow good food safety practices at all times to keep yourself and your family safe and always remember – when in doubt, throw it out!

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Foodborne Illness and Listeria monocytogenes

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Contact Information

Sharon McDonald, MEd, RD, LDN
  • Extension Educator, Food Safety & Quality
Email:
Phone: 814-865-6953