Listeriosis

Listeriosis is a bacterial infection caused by a gram-positive, motile bacterium, Listeria monocytogenes.^[1] Listeriosis is relatively rare and occurs primarily in newborn infants, elderly patients, and patients who are immunocompromised.^[2]

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Epidemiology

Incidence is 4.4 cases per million population. Pregnant women account for 30% of all cases.^[3] Of all nonperinatal infections, 70% occur in immunocompromised patients.

Pathogenesis

L monocytogenes is ubiquitous in the environment. The main route of acquisition of Listeria is through the ingestion of contaminated food products. Listeria has been isolated from raw meat, dairy products, vegetables, and seafood. Soft cheeses and unpasteurized milk are potential dangers, however post-pasteurization outbreaks of infection from dairy have been from pasteurized milk.^[1]

There are four distinct clinical syndromes:

• Infection in pregnancy: Listeria can proliferate asymptomatically in the vagina and uterus. If the mother becomes symptomatic, it is usually in the third trimester. Symptoms include fever, myalgias, arthralgias and headache. Abortion, stillbirth and preterm labor are complications of this infection.
• Neonatal infection (granulomatosis infantisepticum): There are two forms. One, an early-onset sepsis, with Listeria acquired in utero, results in premature birth. Listeria can be isolated in the placenta, blood, meconium, nose, ears, and throat. Another, late-onset meningitis is acquired through vaginal transmission, although it also has been reported with caesarean deliveries.
• CNS infection: Listeria has a predilection for the brain parenchyma, especially the brain stem, and the meninges. It can cause cranial nerve palsies, encephalitis, meningitis, meningoencephalitis and abscesses. Mental status changes are common. Seizures occur in at least 25% of patients.
• Gastroenteritis: L monocytogenes can produce food-borne diarrheal disease, which typically is noninvasive. The median incubation period is 1-2 days, with diarrhea lasting anywhere from 1-3 days. Patients present with fever, muscle aches, gastrointestinal nausea or diarrhea, headache, stiff neck, confusion, loss of balance, or convulsions.

Diagnosis and treatment

In CNS infection cases, L. monocytogenes can often be cultured from the blood, and always cultured from the CSF. There are no reliable serological or stool tests.

Bacteremia should be treated for 2 weeks, meningitis for 3 weeks, and brain abscess for at least 6 weeks. Ampicillin generally is considered antibiotic of choice; gentamicin is added frequently for its synergistic effects. Overall mortality rate is 20-30%; of all pregnancy-related cases, 22% resulted in fetal loss or neonatal death, but mothers usually survive.^{[citation needed]}

Prevention

Cook all raw food thoroughly. Wash raw vegetables. Avoid consumption of raw milk or raw milk products. Wash hands, knives, and cutting boards after handling uncooked foods. For pregnant or immunocompromised patients, avoid soft cheeses (eg.: feta, Brie, Camembert cheese, bleu); cream cheese, yogurt, and cottage cheese are considered safe. Reheat leftover or ready-to-eat foods (eg.: hot dogs) until steaming hot. Avoid delicatessen foods unless they are thoroughly reheated.^[4]

See also

• List of foodborne illness outbreaks

References