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21 Cards in this Set
- Front
- Back
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What is listeria monocytogenes?
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Foodborne pathogen that causes listeriosis in pregnant women, immunocompromised individuals, and newborns. Disease is rare, but has a high mortality rate with infection.
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Describe the structure of listeria.
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Gram positive, coccobacilli, non-spore forming.
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Describe the physiology of listeria.
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catalase positive, facultative anaerobe, motile of 25 degrees C but not 27 degrees C.
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What are the defense barriers of the host that listeria can cross?
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blood brain barrier, placenta, and intestinal mucosa.
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What does it mean to be a facultative intracellular pathogen?
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Can invade cells, but it isn't necessary for the survival of the cell.
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What are internalins?
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Enable L. monocytogenes to invade cells--phagocytes and non-phagocytes alike.
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What are the roles of Listeriolysin O and Phospholipase C?
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enable escape from the phagosome [following phagocytosis].
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What happens once L. monocytogenes is in the cytoplasm of a phagocyte?
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uses ActA to polymerize host cell actin and enable it to move between cells. Polymerized actin pushes bacteria into an adjacent cell on a filopod.
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Describe the cycle of L. monocytogenes.
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1. Endocytosis via internalins. 2. phagosome release via Listeriolysin O and Phospholipase C. 3. Replication. 4. Movement toward cell membrane via ActA. 5. Movement between cells via filipods. 6. Repeat the cycle.
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Where can listeria spread?
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Can enter the blood stream via the gastrointestinal system. From there, it can enter the placenta and the CNS.
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How do people become immune to L. monocytogenes?
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Immunity is cell-mediated. Most people can become immune after infection. Antibodies are not protective, however, low cellular immunity = increased risk of infection. Pregnant women have increased risk of infection.
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Describe the epidemiology of L. monocytogenes.
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Found everywhere, with a higher prevalence in food. It is likely that you need a high amount of L. monocytogenes to get sick.
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What is the mortality rate or L. monocytogenes?
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20-30%
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How many of the infections of L. monoctyogenes are pregnant women?
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30%
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What are some clinical presentations of the disease outside of presentations?
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Bacteremia and meningitis
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When is the mother immunodeficient during pregnancy?
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During weeks 26-30.
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What is the result of L. monocytogenes in pregnant women?
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Symptoms may be flu-like, but the result is 1/4 of pregnancies result in stillborns. 2/3 surviving infants have neonatal listeriosis.
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What is early onset neonatal listeriosis?
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Infection occurs in utero, meaning that the L. monocytogenes crosses the placenta in utero. This is associated with sepsis and meningitis.
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What is late onset neonatal listeriosis?
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May be adquired by vagina at birth. They may carry L. monocytogenes symptomless in their gut or vagina. Late onset is usually associated with meningitis.
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How do you treat L. monocytogenes?
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Penicillins, or macrolides if you are allergic to penicillins.
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How to you prevent L. monocytogenes?
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Avoid high-risk foods if you are immunodeficient or in the high-risk group.
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