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VNAA - Visiting Nurse Associations of America
VNAA The Voice of Home Healthcare

Listeria
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ListeriaListeriosis is a bacterial disease usually manifested as meningoencephalitis and/or septicemia in newborns and adults. It is caused by Listeria monocytogenes, a gram-positive rod shaped bacterium. In the United States, an estimated 2,500 persons become seriously ill with listeriosis each year. Of these, 500 die. About 30% of clinical cases occur within the first three weeks of life; in nonpregnant adults, infection occurs mainly after 40. At increased risk are:
  • Pregnant women- They are about 20 times more likely than other healthy adults to get listeriosis. About one-third of listeriosis cases happen during pregnancy.
  • Newborns - Newborns rather than the pregnant women themselves suffer the serious effects of infection in pregnancy.
  • Persons with weakened immune systems
  • Persons with cancer, diabetes, or kidney disease
  • Persons with AIDS - They are almost 300 times more likely to get listeriosis than people with normal immune systems.
  • Persons who take glucocorticosteroid medications
  • The elderly

Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.

EPIDEMIOLOGY

RESERVOIR
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 bacterium without appearing ill and can contaminate foods of animal origin such as meats and dairy products. Unlike most other foodborne pathogens, Listeria tends to multiply in contaminated refrigerated foods.

MODE OF TRANSMISSION

Ingestion is the primary mode of transmission. The bacterium is 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 bacterium.

Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy. Although healthy persons may consume contaminated foods without becoming ill, those at increased risk for infection can probably get listeriosis after eating food contaminated with even a few bacteria. Persons at risk can prevent Listeria infection by avoiding certain high-risk foods and by handling food properly.

Listeria is killed by pasteurization and cooking; however, in certain ready-to-eat foods such as hot dogs and deli meats, contamination may occur after cooking but before packaging.

TREATMENT

When infection occurs during pregnancy, antibiotics, such as penicillin or ampicillin alone or with aminoglycosides ,( TMP-SMX or erythromycin for penicillin allergic people), given promptly to the pregnant woman can often prevent infection of the fetus or newborn. Babies with listeriosis receive the same antibiotics as adults, although a combination of antibiotics is often used until physicians are certain of the diagnosis. Even with prompt treatment, some infections result in death. This is particularly likely in the elderly and in persons with other serious medical problems.

INCUBATION PERIOD
Outbreak cases have occurred 3-70 days following a single exposure to a contaminated product. Generally, the average incubation is estimated to be 3 weeks.

METHODS OF CONTROL

General recommendations:

• Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.

• Wash raw vegetables thoroughly before eating.

• Keep uncooked meats separate from vegetables and from cooked foods and ready-to-eat foods.

• Avoid unpasteurized (raw) milk or foods made from unpasteurized milk.

• Wash hands and utensils after handling uncooked foods. Thoroughly clean and disinfect cutting boards and food preparation surfaces.

• Consume perishable and ready-to-eat foods as soon as possible.

Recommendations for persons at high risk, such as pregnant women and persons with weakened immune systems, in addition to the recommendations listed above:

• Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot.

• Avoid getting fluid from hot dog packages on other foods, utensils, and food preparation surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats.

• Do not eat soft cheeses such as feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pastuerized milk.

• Do not eat refrigerated pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads may be eaten.

• Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole. Canned or shelf-stable smoked seafood may be eaten.


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