Listeriosis
Listeriosis is an bacterial infection caused by a gram-positive motile bacterium, Listeria monocytogenes. Listeriosis is relatively rare and occurs primarily in newborn infants, elderly patients, and patients who are immunocompromised.
Epidemiology
Incidence is 7.4 cases per million population. Annually, 1850 cases are reported in the US. Pregnant women account for 27% of all cases. Of all nonperinatal infections, 70% occur in immunocompromised patients.
Pathophysiology
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 have been the most frequently culprits.
Features
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 GU 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 cesarean deliveries.
- CNS infection: Listeria has a predilection for the brain parenchyma, especially the brain stem, and the meninges. Mental status changes are common. Seizures occur in at least 25% of patients. Cranial nerve palsies, encephalitis, meningitis and abscesses occur.
- 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, myalgias, and diarrhea.
Diagnosis
L monocytogenes can often be cultured from the blood, and always cultured from the CSF. There are no reliable serological or stool tests.
Treatment
Bacteremia should be treated for 2 weeks, meningitis for 3 weeks, and brain abscess for at least 6 weeks. Ampicillin generally is considered the preferred agent, but other agents may be acceptable. Gentamicin is added frequently for synergy.
Prognosis
The overall mortality rate is 20-30%. Of all pregnancy-related cases, 22% resulted in fetal loss or neonatal death, but mothers usually survive.
Prevention
Recommended by the CDC:
- Cook all raw food thoroughly. Wash raw vegetables. Avoid consumption of raw milk or milk products. Wash hands, knives, and cutting boards after handling uncooked foods. For pregnant or immunocompromised patients, avoid soft cheeses (eg, feta, Brie, Camembert, bleu). Cream cheese, yogurt, and cottage cheese are allowed. Reheat leftover or ready-to-eat foods (eg, hot dogs) until steaming hot. Avoid delicatessen foods unless they are thoroughly reheated.
