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Classification and external resources

Listeria monocytogenes
ICD-10 A32.
ICD-9 027.0
DiseasesDB 7503
MedlinePlus 001380
eMedicine med/1312 ped/1319

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]

The symptoms of listeriosis usually last 7-10 days. The most common symptoms are fever and muscle aches and vomitting. Nausea and diarrhea are less common symptoms. If the infection spreads to the nervous system it can cause meningitis, an infection of the covering of the brain and spinal cord. Symptoms of meningitis are headache, stiff neck, confusion, loss of balance, and convulsions.[3][4]

Listeriosis has a very low incidence in humans. However, pregnant women are much more likely than the rest of the population to contract it. Infected pregnant women may have only mild, flulike symptoms. However, infection in a pregnant woman can lead to early delivery, infection of the newborn, and death of the baby.[5]

In veterinary medicine, listeriosis can be a quite common condition in some farm outbreaks. It can also be found in wild animals; see listeriosis in animals.



Incidence in 2004–2005 was 2.5–3 cases per million population a year in the USA, where pregnant women accounted for 30% of all cases.[6] Of all nonperinatal infections, 70% occur in immunocompromised patients. Incidence in the USA has been falling since the 1990s, in contrast to Europe where changes in eating habits have led to an increase during the same time. In Sweden, it has stabilized at around 5 cases per annum per million population, with pregnant women typically accounting for 1–2 of some 40 total yearly cases.[7]

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. Miscarriage, stillbirth and preterm labor are complications of this infection. Symptoms last 7-10 days.
  • 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.
  • Central nervous system (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 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 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, unpasteurized milk and unpasteurised pâté are potential dangers; however, some outbreaks involving post-pasteurized milk have been reported.[1]

Rarely listeriosis may present as cutaneous listeriosis. This infection occurs after direct exposure to L. monocytogenes by intact skin and is largely confined to veterinarians who are handling diseased animals, most often after a listerial abortion.[8]

Diagnosis and treatment

Listeria monocytogenes grown on Biorad RAPID'L.Mono Agar

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.[9].[citation needed]


The main means of prevention is through the promotion of safe handling, cooking and consumption of food. This includes washing raw vegetables and cooking raw food thoroughly, as well as reheating leftover or ready-to-eat foods like hot dogs until steaming hot. [10]

Another aspect of prevention is advising high-risk groups such as pregnant women and immunocompromised patients to avoid unpasteurized pâtés and foods such as soft cheeses like feta, Brie, Camembert cheese, and bleu. Cream cheeses, yogurt, and cottage cheese are considered safe. In the United Kingdom, advice along these lines from the Chief Medical Officer posted in maternity clinics led to a sharp decline in cases of listeriosis in pregnancy in the late 1980s.[11]

Intralytix, a Maryland-based biotechnology firm, has received FDA approval for a product, ListShield, that is proven effective in eliminating Listeria monocytogenes bacteria using a preparation containing six listeria-specific bacteriophages. The product is an aqueous solution that is sprayed directly onto food or surfaces used in food production. It is odorless and tasteless.

See also


  1. ^ a b Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9. 
  2. ^ Hof H (1996). Listeria Monocytogenes in: Baron's Medical Microbiology (Baron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1. 
  3. ^ [ University of Michigan Health System, Women's health advisor
  4. ^
  5. ^ [ University of Michigan Health System, Women's health advisor
  6. ^ Center for Infectious Disease Research & Policy, University of MinnesotaListeriosis
  7. ^ Smittskyddsinstitutet – för listeriainfektion
  8. ^ Swaminathan B, Gerner-Smidt P. 2007. The epidemiology of human listeriosis. Microbes Infect. 10:1236-43.
  9. ^ [1]
  10. ^ "Listeriosis". CDC: Division of Bacterial and Mycotic Diseases. Retrieved 2006-05-02. 
  11. ^ Skinner et al. (1996). Listeria: the state of the science Rome 29–30 June 1995 Session IV: country and organizational postures on Listeria monocytogenes in food Listeria: UK government's approach. 7. Food control. pp. 245–247. 

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