listeria risk factors prevention

Featuring Tamara Rhodes, MS, RD, LDN

Listeriosis is a foodborne illness that is caused by ingesting food or beverages contaminated with the bacterium Listeria monocytogenes. About 1,600 cases of listeriosis are documented each year, with a fatality rate of about 16 percent.

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Who is most at risk for getting listeriosis?

Listeriosis is currently the third leading cause of death from food poisoning in the United States. Unlike other foodborne pathogens, the Listeria monocytogenes bacterium can cross the placenta of a pregnant woman and also infect a fetus. The population groups considered to be the most vulnerable to a Listeria infection are pregnant women, newborn infants, adults aged 65 and older and individuals with weakened immune systems. Older adults are four times as likely as younger adults to contract listeriosis over half of those diagnosed with a Listeria infection are age 65 or over. The risk for listerosis increases tenfold in both pregnant women and cancer patients, and people on dialysis are 50 times more likely to become infected.

Symptoms of a Listeria infection usually begin about one to four weeks after exposure. Listeriosis often presents with flu-like symptoms, which may include fever, muscle aches, diarrhea and mild nausea. Some people, particularly elderly adults, may experience a headache, stiff neck, confusion, loss of balance or convulsions. Infection during pregnancy can result in miscarriage, stillbirth, low birth weight and/or preterm labor. In immunocompromised individuals and neonates, listeriosis commonly manifests as an invasive infection, such as sepsis, meningitis, meninencephalitis or granulomatosis infantiseptica.

Listeriosis is diagnosed through a bacterial culture taken from a body tissue or fluid (blood, cerebrospinal fluid, placenta). A stool culture is not recommended as a screening tool for listeriosis. Once diagnosed, the Listeria infection is treated with antibiotics.

How can you prevent listeriosis?

Listeria outbreaks have been traced to deli meats, hot dogs, soft cheeses, celery, sprouts, cantaloupe, ice cream and raw eggs. You can use the following tips to help protect yourself from potential exposure to the Listeria monocytogenes bacterium.

1. Avoid eating cheese made with unpasteurized milk.

Cheeses made with unpasteurized milk are 50 to 160 times more likely to cause a Listeria infection than cheeses made with pasteurized milk. Although the pasteurization of milk kills the Listeria monocytogenes bacterium, dairy products made from pasteurized milk can still become contaminated if they are produced in facilities with unsanitary conditions. Always check the product label or with a restaurant to verify that cheese came from a pasteurized source. Extra caution should be exercised with the following soft cheeses:

  • Brie
  • Camembert
  • Feta
  • Blue cheese
  • Gorgonzola
  • Farmer’s cheese
  • Blue-veined
  • Mexican-style soft cheeses (queso fresco, queso blanco, queso panela)

2. Never drink unpasteurized (raw) milk or eggnog.

3. Purchase whole melons and clean the skin well before slicing. Melons that have been cut should be eaten right away or placed in the refrigerator. Cut melon should be refrigerated at 41° F or colder and for no more than seven days. Throw away any cut melon left at room temperature for more than four hours.

4. Avoid eating sprouts unless thoroughly cooked. Sprouts (alfalfa, clover, radish, mung bean) require warm and humid conditions in order to sprout and grow. However, this environment is also ideal for the growth of bacteria. Individuals at a high risk for listeriosis (pregnant women, older adults, people with weakened immunity) should not eat raw or lightly cooked sprouts of any kind. Fully cooked sprouts are considered to be safe, as thorough cooking will kill the harmful bacteria.

  • Both home-grown and commercially-produced sprouts can contain Listeria monocytogenes
  • Rinsing sprouts will not remove bacteria
  • If eating out, request that raw sprouts not be added to your food
  • If you purchase a ready-made sandwich, salad or Asian entrée, check to ensure that it does not contain raw sprouts

5. Safely store all processed meats in the refrigerator.

  • Opened packages of hot dogs should not be stored for longer than one week. Unopened packages should not be stored for longer than two weeks
  • Opened packages of lunch meat or meat sliced at a local deli should not be stored for longer than three to five days. Factory-sealed, unopened packages of lunch meat or deli meat should not be stored for longer than two weeks

6. Do not allow the juices from meat packages (hot dogs, lunch meat, or deli meats) to get on other foods, utensils or food preparation surfaces. Wash your hands thoroughly after handling hot dogs, lunch meat and deli meat.

7. High-risk populations should not eat hot dogs, lunch meat, cold cuts, other deli meat (such as bologna) or fermented/dry sausages unless the meat has been heated to steaming hot or an internal temperature of 165° F just before serving.

  • Avoid chef’s salads unless you prepare them yourself and have the capability to heat the meat
  • If eating at a sub shop or ordering a sandwich at a restaurant, request that your entire sandwich be toasted

8. Do not eat refrigerated pâté or meat spreads from a deli/meat counter or from the refrigerated section of a grocery store. Foods that do not need refrigeration, like canned or shelf-stable pâté and meat spreads, are safe to eat. These foods should be refrigerated immediately after opening.

  • A food is considered to be shelf-stable if it can be safely stored at room temperature. Eating canned and shelf-stable tuna, salmon, or sardines does not increase the risk of Listeria poisoning
  • Keep in mind that not all canned foods are shelf-stable – some canned foods are labeled “Keep Refrigerated”

9. Do not consume refrigerated smoked seafood unless it is canned, shelf-stable or in a cooked dish such as a casserole. Refrigerated smoked seafood items are often labeled as “nova-style,” “lox,” “kippered,” “smoked” or “jerky” and typically found at seafood or deli counters of grocery stores and delicatessens.

10. Avoid eating raw or undercooked meat, poultry or fish. This includes:

  • Rare hamburger
  • Sushi, tartare, and sashimi
  • Raw oysters
  • Pink chicken or turkey

11. Choose hard ice cream and gelato over soft serve ice cream. Soft serve ice cream is typically kept at a higher temperature than other frozen desserts, and does not under the freezing process, which kills bacteria. Soft serve ice cream also has a high protein and moisture content, which may enable bacteria to grow. In addition, soft serve dispensing machines are often poorly maintained and not cleaned well, which poses the risk of contamination.

If you are concerned that you have a  listeria infection, please contact our 2/47 Nurse Line at 1-866-968-7731. They can help you evaluate your symptoms and provide you advice on necessary treatment to seek.

About UPMC Harrisburg

UPMC Harrisburg is a nationally recognized leader in providing high-quality, patient-centered health care services in south central PA. and surrounding rural communities. UPMC Harrisburg includes seven acute care hospitals and over 160 outpatient clinics and ancillary facilities serving Dauphin, Cumberland, Perry, York, Lancaster, Lebanon, Juniata, Franklin, Adams, and parts of Snyder counties. These locations care for more than 1.2 million area residents yearly, providing life-saving emergency care, essential primary care, and leading-edge diagnostic services. Its cardiovascular program is nationally recognized for its innovation and quality. It also leads the region with its cancer, neurology, transplant, obstetrics-gynecology, maternity care, and orthopaedic programs.

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