Listeriosis can cause various forms of infection in humans, such as bacteremia, meningitis, encephalitis, dermatitis, intrauterine and neonatal infections, or rare endocarditis caused by Listeria sp. Symptoms vary depending on the damage to various organs and systems. An intrauterine infection can lead to fetal death. The diagnosis is confirmed by laboratory methods. Treatment includes penicillin, ampicillin (often with aminoglycosides) and trimethoprim/sulfamethoxazole.
Listeria is small, non-acid-resistant, capsule-free, non-spore-forming, beta-hemolytic, aerobic and optionally anaerobic gram-positive bacilli that have characteristic slight mobility. They are distributed in the environment and in the intestines of humans. They are present in mammals, birds, arachnids, and crustaceans. There are several species of Listeria, but only L. monocytogenes is the main pathogen for humans.
In the United States, the average annual level of laboratory-confirmed listeriosis is about 2.6 cases per 1,000,000 people. Its peak is during the summer. The incidence rates are highest in newborns, adults ≥ 60 years of age, and people with weakened immunity, including patients with HIV / AIDS. Listeriosis is 300 times more common among patients with HIV / AIDS than among the general population.
Since L. monocytogenes is common in the environment. There is a high likelihood of contamination during the food production process. Almost all types of food can contain and transmit L. monocytogenes, but the infection is usually transmitted by eating infected dairy products, raw vegetables, meat or, especially, frozen foods that do not require preparation before consumption. Contamination contributes to the ability of L. monocytogenes to survive and grow at the temperature of the refrigerator. Infection can also be transmitted through direct contact and during the extermination of infected animals.
L. monocytogenes multiplies inside the cell. The control of listeriosis is achieved due to cellular immunity. Therefore, people in the following groups fall into the high-risk group:
- immunocompromised patients;
- the elderly.
Pregnant women are also at risk because the infection can develop during pregnancy. It can be transmitted to the fetus during the antenatal period and during childbirth. It can lead to abortion or fetal death.
Listeria is a common cause of neonatal bacterial meningitis.
Primary listeriosis bacteremia rarely occurs. It is manifested by high body temperature without local symptoms and signs. Endocarditis, peritonitis, osteomyelitis, septic arthritis, cholecystitis, and pleuropneumonia may develop. After ingestion of contaminated food, gastroenteritis with fever may develop. Listeriotic bacteremia during pregnancy can cause an intrauterine infection, chorioamnionitis, premature birth, intrauterine death, or a neonatal infection of the fetus.
Listeria-induced meningitis occurs in approximately 20% of cases in newborns and in patients> 60 years of age. In 20% of cases, signs of encephalitis, diffuse encephalitis, or, rarely, rhombencephalitis and abscesses may occur; rhombencephalitis manifests itself as altered consciousness, cranial nerve palsy, cerebellar signs, and motor or sensory insufficiency.
Oculoglandular listeriosis can cause ophthalmitis and an increase in regional lymph nodes (Parinaud syndrome). Conjunctival inoculations can develop on the background of this symptomatology, which in the absence of isotropic treatment can transfer into bacteremia and meningitis.
The diagnosis of listeriosis is confirmed by the isolation of L. monocytogenes culture from the blood and CSF. Laboratory staff should be informed of suspected L. monocytogenes, as Listeria can easily be mistaken for diphtheroids.
For all listeriosis infections, IgG titers reach a maximum within 2–4 weeks after the disease onset.
Ampicillin or penicillin G, usually with an aminoglycoside is prescribed.
Listeriotic meningitis is effectively treated with ampicillin, 2 g intravenously every 4 hours. Most experts recommend adding gentamicin (1 mg/kg intravenously every 8 hours) based on in vitro synergism. Cephalosporins are ineffective. Pathogen-specific antibiotic therapy is prescribed as the treatment of neonatal meningitis, Bacterial meningitis in the newborn.
With endocarditis and primary listeriosis bacteremia, ampicillin is used intravenously 2 g every 4 hours in combination with gentamicin (for synergy) for up to 6 weeks (with endocarditis) or 2 weeks (with bacteremia) after a decrease in temperature.
With oculoglandular listeriosis and listeriotic dermatitis, erythromycin 10 mg/kg every 6 hours is prescribed, treatment lasts up to 1 week after lowering the temperature.
Cephalosporins do not have in vitro property, therefore, they should not be used; vancomycin inefficiency has also been reported. The drug of choice is Trimethoprim/sulfamethoxazole 5/25 mg/kg every 8 hours. Linezolid is effective in vitro, but clinical experience is insufficient.
Since food infection of L. monocytogenes is widespread, the bacillus can multiply at low temperatures in the refrigerator, pathogen contamination can increase significantly during the storage period of food. This problem is of particular concern when food products (for example, processed foods stored in a refrigerator) are used as food without further preparation. Therefore, food hygiene is very important, especially for people at risk (for example, people with weakened immune systems, pregnant women, the elderly). At-risk individuals should avoid the following foods:
- soft cheeses (e.g. feta, brie, camembert);
- fast food (e.g. hot dogs, deli meats, meat pastes) if they are not heated to 165 °F or are not steamed before serving;
- chilled smoked, salted, dried, seafood without prior hot processing;
- raw (unpasteurized) milk.