Listeriosis

Description

Listeriosis is a serious acute bacterial infection that most commonly presents as sepsis or infection of the central nervous system, including meningitis and encephalitis. Less commonly, it may cause endocarditis or conjunctivitis.

Causative Agent

Listeriosis is caused by the bacterium Listeria monocytogenes.

Transmission

Listeria monocytogenes infects both humans and animals. In livestock, particularly sheep and cattle, it commonly causes sepsis and meningoencephalitis. Infected animals shed the bacteria in milk, urine, feces, and nasal secretions. The organism is widely distributed in the environment and can be found in soil, water, dust, and silage.

Humans become infected through direct contact with infected animals, consumption of contaminated food, or vertical transmission from mother to fetus during pregnancy. Although most cases are sporadic, foodborne outbreaks may occur. High-risk foods include soft cheeses, unpasteurized milk and dairy products, ice cream, undercooked meat, smoked fish, fresh vegetables, and ready-to-eat salads.

Individuals at greatest risk include immunocompromised patients (such as those with HIV/AIDS, malignancy, or those receiving corticosteroids or immunosuppressive therapy), pregnant women, neonates younger than 1 month of age, and adults older than 70 years. Most infections occur during the summer months.

Symptoms

Listeriosis is particularly dangerous during pregnancy and may occur at any stage of gestation. Symptoms include fever, headache, myalgia, back pain, and diarrhea. Infection may result in miscarriage, preterm delivery, or stillbirth.

Congenital listeriosis may present at birth with jaundice, purulent conjunctivitis, pneumonia, meningitis, or encephalitis. A characteristic feature is the presence of disseminated granulomas in multiple organs (granulomatosis infantiseptica). Infants infected at birth or during delivery may initially appear healthy but can develop life-threatening disease within several days or weeks.

Diagnosis

The diagnosis is confirmed by isolation of Listeria monocytogenes using bacterial culture. Specimens may include blood, cerebrospinal fluid, urine, conjunctival or nasal swabs, and infected tissue samples.

Treatment

Treatment consists of antibiotic therapy targeting Listeria monocytogenes. The standard regimen is ampicillin combined with gentamicin, although gentamicin is generally avoided during pregnancy. Ampicillin may be replaced by penicillin, and in patients with β-lactam allergy, trimethoprim-sulfamethoxazole or vancomycin may be used. Analgesics and antipyretics may be administered for symptomatic relief. Severe cases require treatment in an intensive care unit.

Prevention

Listeriosis is a notifiable infectious disease. Proper food hygiene is essential for prevention. Pregnant women and immunocompromised individuals should avoid high-risk foods, including soft cheeses made from unpasteurized milk, pâté, undercooked poultry, and ready-to-eat foods that may be contaminated with Listeria.

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology