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Biology LibreTexts

15.17J: Listeriosis

  • Page ID
    12306
  • Listeriosis is a bacterial infection caused by a Gram-positive, motile bacterium called Listeria monocytogenes.

    Learning Objectives

    • Discuss the mechanism of action for listeriosis

    Key Points

    • Listeriosis has a low incidence in humans and occurs in pregnant women, newborn infants, elderly patients, and patients who are immunocompromised.
    • Listeria can invade through unusually tough barriers in humans: the blood-brain barrier and the feto-placental barrier, which contain high levels of cadherin protein on their membrane.
    • The main route of acquisition of Listeria is through the ingestion of contaminated food products.

    Key Terms

    • incidence: a measure of the risk that a person develops a new condition within a specified period of time, usually a year
    • listeriosis: An infectious disease of humans and animals caused by the bacteria Listeria monocytogenes and Listeria ivanovii, often through contaminated food.
    • meningitis: Inflammation of the meninges, characterized by headache, neck stiffness and photophobia and also fever, chills, vomiting, and myalgia.
    • cadherin: Any of a class of transmembrane proteins important in maintaining tissue structure.
    • blood-brain barrier: a structure in the central nervous system (CNS) that keeps various substances found in the bloodstream out of the brain while allowing in the substances essential to metabolic function

    Listeriosis is a bacterial infection caused by a Gram-positive, motile bacterium, Listeria monocytogenes. Listeriosis has a low incidence in humans and occurs in pregnant women, newborn infants, elderly patients, and patients who are immunocompromised. Pregnant women are the most susceptible and infection can lead to early delivery, infection of the newborn, and death of the baby.

    image
    Figure: Listeria monocytogenes: A bacterial infection caused by a Gram-positive, motile bacterium, Listeria monocytogenes which is shown here on a blood agar plate.

    The symptoms of listeriosis usually last 7–10 days, with the most common symptoms being fever, muscle aches, and vomiting. Diarrhea is another symptom, but less common. If the infection spreads to the nervous system it can cause meningitis, an infection of the covering of the brain and spinal cord.

    Listeria originally evolved to invade membranes of the intestines, as an intracellular infection, and developed a chemical mechanism to do so. This involves a bacterial protein “internalin” which attaches to a protein on the intestinal cell membrane “cadherin. ” These adhesion molecules are also to be found in two other unusually tough barriers in humans – the blood-brain barrier and the feto-placental barrier, and this may explain the apparent affinity that Listeria has for causing meningitis and affecting babies in-utero. Particular strains of a food-borne bacteria are able to invade the heart, leading to serious and difficult-to-treat heart infections.

    Listeria monocytogenes is ubiquitous in the environment. The main route of acquisition is by the ingestion of contaminated food products. Listeria has been isolated from raw meat, dairy products, vegetables, fruit and seafood. Soft cheeses, unpasteurized milk and unpasteurised pâté are potential dangers too. The main 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. Another preventative measure is to advise high-risk groups such as pregnant women and immunocompromised patients to avoid unpasteurized pâtés and foods such as soft cheeses.

    In the advent of listeriosis, bacteremia should be treated for two weeks, meningitis for three weeks, and brain abscess for at least six weeks. Ampicillin generally is considered the antibiotic of choice and gentamicin is added frequently for its synergistic effects. About 10 percent of serious listeria infections involve cardiac infections that are difficult to treat, with more than one-third proving fatal.

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