Listeriosis is an infection that can occur when a person eats food that has been contaminated with bacteria called Listeria monocytogenes (L monocytogenes).
The bacteria L 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 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
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 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 one half of infants infected at or near birth 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 infection (meningitis)
- Lung infection (pneumonia)
- Blood infection (septicemia)
- Gastrointestinal infection (gastroenteritis, diarrhea)
Or it may occur in a milder form as:
Exams and Tests
Laboratory tests may be done to detect the bacteria in amniotic fluid, blood, feces, and urine. A spinal fluid (cerebrospinal fluid or CSF) culture will be performed if a spinal tap is performed.
Antibiotics (including ampicillin or trimethoprim-sulfamethoxazole) are prescribed to kill the bacteria.
Listeriosis in a fetus or infant is often fatal. Healthy older children and adults are more likely to survive. The illness is less serious if it only affects the gastrointestinal system. Brain or spinal infections have worse outcomes.
Infants who survive listeriosis may have long-term brain and nervous system (neurologic) damage and delayed development.
When to Contact a Medical Professional
Call your health care provider if you or your child develops symptoms of listeriosis.
Foreign food products, such as nonpasteurized soft cheeses, have also led to outbreaks of listeriosis. Always cook food thoroughly.
Wash your hands thoroughly after touching pets, farm animals, and handling animal feces.
Pregnant women may want to visit the Centers for Disease Control and Prevention (CDC) website for information on food precautions: www.cdc.gov/listeria/prevention.html.
Listerial infection; Granulomatosis infantisepticum; Fetal listeriosis
Johnson JE, Mylonakis E. Listeria monocytogenes. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 206.
Kollman TR, Mailman TL, Bortolussi R. Listeriosis. In: Wilson CB, Nizet V, Maldonado YA, Remington JS, Klein JO, eds. Remington and Klein's Infectious Diseases of the Fetus and Newborn Infant. 8th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 13.
Review Date 9/1/2021
Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.