Listeriosis

Definition

Listeriosis is a dangerous infection caused by eating food contaminated with bacteria called Listeria monocytogenes (L. monocytogenes).

Causes, incidence, and risk factors

According to the U.S. Centers for Disease Control and Prevention, listeriosis is an important public health problem in the United States.

The bacteria (L. monocytogenes) that cause this disease are common in wild animals, domesticated animals, and in soil and water. The bacteria make many animals sick and commonly lead 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. Pregnant women, developing fetuses, newborns, and adults with weakened immune systems are at increased risk. 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).

Infection in early pregnancy generally leads to 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.

Symptoms

In infants, symptoms of listeriosis may be seen in the first few days of life and may include:

• Loss of appetite
• Lethargy
• Jaundice
• Vomiting
• Respiratory distress (usually pneumonia)
• Shock
• Skin rash
• Increased pressure inside the skull (due to meningitis) possibly causing suture separation

Late-appearing infection in the infant (symptoms appear age 5 days or older) and infection in children is often seen as meningitis.

In adults, the disease may take many forms depending on what organ or organ systems are infected. It may occur as meningitis, pneumonia, septicemia, and endocarditis, or in milder form as abscesses, skin lesion, and conjunctivitis.

If a pregnant woman becomes infected, it can lead to:

• Stillbirth
• Death of a newborn within a few hours of birth

Signs and tests

Laboratory tests may be done to detect the bacteria in amniotic fluid, blood, feces, and urine. A CSF culture may be performed.

Note: There is no way, without testing, to know if meningitis is due to listeria or another cause.

Treatment

Antibiotics are prescribed to kill the bacteria that are causing the infection.

Expectations (prognosis)

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.

Complications

Infants who survive listeriosis may have long-term neurological damage and delayed development.

Calling your health care provider

Call your health care provider if you or your child develop symptoms of Listeriosis.

Prevention

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 consumption of soft cheeses, deli meats, and cold salads from salad bars. Foreign food products such as nonpasteurized soft cheeses have also been implicated in outbreaks of listeriosis. Food should always be adequately cooked.

References

Lorber B. Listeriosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 316.

Centers for Disease Control and Prevention (CDC). Preliminary FoodNet Data on the Incidence of Infection with Pathogens Transmitted Commonly Through Food -- 10 States. MMWR Morb Mortal Wkly Rep. 2009;58(13);333-337.

Centers for Disease Control and Prevention (CDC). Diagnosis and management of foodborne illnesses: a primer for physicians and other health care professionals. MMWR Morb Mortal Wkly Rep. 2004;53(RR-4);1-33.