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Listeriosis is an infection that can occur when a person eats food that has been contaminated with bacteria called Listeria monocytogenes (L. monocytogenes).
The bacterium Listeria monocytogenes is found in wild animals, domesticated animals, and in soil and water. These bacteria make many animals sick, leading to miscarriage and stillbirth in domestic animals.
Vegetables, meats, and other foods you eat can get infected with the bacteria if they come in contact with contaminated soil or manure. Raw milk or products made from raw milk may carry these bacteria.
If you eat the contaminated products, you may get sick. The following people are at increased risk:
- Adults over age 50
- Adults with a weakened immune system
- Developing fetuses
- Pregnant women
The bacteria most often cause a gastrointestinal illness. In some cases, you can develop a blood infection (septicemia) or inflammation of the covering of the brain (meningitis). Infants who are 5 days or older and children often have meningitis.
Infection in early pregnancy may cause a miscarriage. The bacteria may cross the placenta and infect the developing baby. Infections in late pregnancy may lead to stillbirth or death of the infant within a few hours of birth. About half of infants infected at or near term will die.
In adults, the disease may take many forms, depending on what organ or organ systems are infected. It may occur as:
- Heart infection (endocarditis)
- Brain or spinal fluid injection (meningitis)
- Lung infection (pneumonia)
- Blood infection (septicemia)
Or it may occur in a milder form as:
In infants, symptoms of listeriosis may be seen in the first few days of life and may include:
Exams and Tests
Laboratory tests may be done to detect the bacteria in amniotic fluid, blood, feces, and urine. A CSF culture will be performed if a spinal tap is performed.
Antibiotics (including ampicillin or trimethoprim-sulfamethoxazole) are prescribed to kill the bacteria that are causing the infection.
Listeriosis in a fetus or infant results in a poor outcome with a high death rate. Healthy older children and adults have a lower death rate. Gastrointenstinal infections in healthy persons are rarely fatal.
Infants who survive listeriosis may have long-term brain and nervous system (neurological) damage and delayed development.
When to Contact a Medical Professional
Call your health care provider if you or your child develop symptoms of listeriosis.
Pregnant women should avoid contact with wild and domestic animals. Listeria is well controlled in American food products, but food-associated outbreaks have occurred.
Pregnant women should avoid eating soft cheeses, deli meats, and cold salads from salad bars. Foreign food products such as non-pasteurized soft cheeses have also led to outbreaks of listeriosis. Always cook food thoroughly.
Baltimore RS. Listeria monocytogenes. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 181.
Bennett L. Listeria monocytogenes. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2009:chap 207.
Reviewed By: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.