Listeriosis

Listeriosis is an infectious disease caused by the gram-positive, catalase-positive, rod-shaped, and facultative intracellular motile bacterial pathogen L monocytogenes. 

It is most commonly transmitted to humans through ingestion of contaminated food such as cold cuts, contaminated produce, and especially unpasteurized milk products. 

L monocytogenes invades  host cells via a virulence factor protein internalin A.

Protein internalin A adheres to the protein E-cadherin in the cells of the intestinal epithelium/blood–brain barrier, and the placenta.

Listeriosis is a reportable disease in the United States.

The median incubation period is 11 days, with 90% of cases occurring within 28 days.

The Morbidity and Mortality Weekly Report revealed 1651 cases of the foodborne illness reported between 2009 2011, with 292 deaths or fetal losses.

More than half of the above cases were in adults age 65 years or older, and 14% pregnancy related.

In the above study 74% of patients younger than 65 years and immunocompromise medical condition.

Soft cheeses, contaminated cantaloupe, precut celery and sushi rolls have been implicated in such infections.

A bacterial infection most commonly caused by Listeria monocytogenes,

L. ivanovii and L. grayi have been reported in certain cases.

Listeriosis primarily causes infections of the central nervous system.

Clinically it appears as sepsis and meningitis. 

Its most common central nervous system (CNS) manifestation is meningoencephalitis. 

Meningoencephalitis symptoms can range from a mild illness with fever and altered mental status to a fulminant course with coma and toxic metabolic encephalitis.

Many patients  with meningoencephalitis do not have signs of meningeal irritation.

CNS infections include meningitis, meningoencephalitis, brain abscess, and cerebritis.

Associated with bacteremia in immunocompromised patients, pregnant women, and those at the extremes of age.

L monocytogenes can migrate from cell to cell via the use of actin comet tails, and proliferates by evading the phagosome by  listeriolysin phospholipase O).

Listeriolysin O also deactivates  T-cell receptors and impairing T-cell activation by antigen-presenting cells.

Gastroenteritis may occur in healthy persons who have ingested a large inoculum of the organism.

Listeria is ubiquitous in the environment.

Incidence approximately 2.5–3 cases per million population a year in the United States.

Incidence in the U.S. has been falling since the 1990s,

Of nonperinatal infections, 70% occur in immunocompromised patients.

Disease manifestation occurs most commonly in high-risk groups such as immunocompromised, elderly, or pregnant persons. 

More than 69% of cases in nonpregnant adults occur in persons with cancer, with HIV disease, who are organ transplant recipients, or who are on corticosteroid therapy.

Pregnant women account for 30% of all cases.

Primarily transmitted via the oral route after ingestion of contaminated food products.

Following ingestion the organism penetrates the intestinal tract to cause systemic infections.

Disease may manifest as much as two months after eating contaminated food.

Listeriosis is asymptomatic in the vast majority of immunocompetent individuals. 

Symptoms can be mild flulike exanthems or febrile gastroenteritis. 

It can be invasive and spread beyond the gastrointestinal tract and may result in severe symptoms.

Diagnosis requires the isolation of the organism from the blood and/or the cerebrospinal fluid.

No treatment is required in immunocompetent persons with mild constitutional symptoms.

Antibiotic indications for treatment include CNS infection, bacteremia, and endocarditis. 

First-line antibiotic treatment:

 ampicillin or penicillin G, usually in combination with gentamicin for synergistic properties.

Second-line treatment: with macrolides, fluoroquinolones, trimethoprim-sulfamethoxazole, or vancomycin.

Primarily affects older adults, persons with weakened immune systems, pregnant women, and newborns, and rarely in patients without these risk factors.

Risk factors include any other systemic inflammation that alters the mucosal antigenic properties. 

Patients present with fever and myalgias often preceded by diarrhea or other gastrointestinal symptoms.

Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions.

Pregnant women generally experience only a mild, flu-like illness, however, infections can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.

Healthy individuals exposed to a very large dose of Listeria can develop a non-invasive illness with diarrhea and fever.

Listeria monocytogenes is ubiquitous in the environment.

The main route of acquisition of Listeria is through the ingestion of contaminated food products such as raw meat, dairy products, vegetables, fruit and seafood.

Rarely listeriosis may present as cutaneous listeriosis after direct exposure to L. monocytogenes by intact skin and is largely confined to veterinarians who are handling diseased animals.

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 for Listeriosis.

Prevention is through the promotion of safe handling, cooking and consumption of food.

Food handling includes the washing of raw vegetables, cooking raw food thoroughly, and reheating leftover or ready-to-eat foods until steaming.

High-risk groups such as pregnant women and immunocompromised patients should avoid unpasteurized pâtés and foods such as soft cheeses.

Treatment: Ampicillin generally is considered the antibiotic of choice.

Gentamicin is added frequently for its synergistic effects.

The duration of treatment for bacteremia is 2 weeks, meningitis is 3 weeks, and brain abscess for at least 6 weeks.

Overall mortality rate is 20–30%.

22% of cases in pregnancy results in fetal loss or neonatal death, but mothers usually survive.

Listeriosis in pregnancy most often occurs in the third trimester and can lead to fetal death, premature birth, or infected newborns. 

There are four distinct clinical syndromes:

Infection in pregnancy.

Listeria can proliferate in the vagina and uterus, asymptomatically, but can clinically manifest in the third trimester.

Symptomatic disease lasting 7-10 days include fever, myalgias, arthralgias and headache, with miscarriage, stillbirth and preterm labor as complications.

Neonatal infection: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.

Listeria has a predilection for the brain, especially the brain stem, and the meninges.

Listeria can cause cranial nerve palsies, encephalitis, meningitis, meningoencephalitis and abscesses.

Mental status changes are common with listeria infection.

Seizures occur in at least 25% of patients with listeriosis.

L. monocytogenes can produce food-borne diarrheal disease, which typically is noninvasive.

The median incubation period is 21 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.

Listeria incidence of cardiac infections caused by Listeria is relatively low, with 7-10% of case reports indicating some form of heart involvement.

About 1,600 cases of listeriosis annually in the United States, with declining incidence.