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| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Listeria species]] |
| − | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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| − | ===Overview===
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| − | *6 species
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| − | *Saprophytes in soil
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| − | *''L. monocytogenes'' and ''L. ivanovii'' are pathogens
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| − | *Carried by sheep and goats and shed in faeces and milk especially during stress
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| − | *Can cause septicaemia, encephalitis and abortion
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| − | *Outbreaks of listeriosis often linked to silage feeding
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| − | ===Characteristics===
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| − | *Small Gram negative rods
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| − | *Catalase positive, oxidase negative
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| − | *Motile
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| − | *Facultative anaerobes
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| − | *''L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures
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| − | *''L. ivanovii produces strong haemolytic zone
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| − | *Small, smooth, transparent colonies after 24 hours incubation
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| − | *Grow on non-enriched media
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| − | ===Pathogenesis and pathogenicity===
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| − | *Infection by ingestion of contaminated feed
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| − | *Bacteria penetrate M cells in intestinal Peyer's patches
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| − | *Spread to tissues via blood and lymph
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| − | *Transplacental transmission in pregnant animals
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| − | *Bacteria may gain entry via breaks in oral or nasal mucosa, migrate in cranial nerves to cause neural signs
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| − | *Causes formation of microabscesses and perivascular lymphocytic cuffs in brainstem
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| − | *''L. monocytogenes'' can replicate within phagocytic and non-phagocytic cell, and pass between cells without being exposed to the immune system
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| − | *Surface proteins known as internalins allow adherence and uptake of the bacteria into cells
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| − | *Listeriolysin produced by virulent strains destroys membranes of phagocytic vacuoles, releasing the bacteria into the cytoplasm
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| − | *Listeria are motile in the cytoplasm
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| − | *Bacteria induce formation of pseudopod projections in the cytoplasmic membrane, which are taken up with the bacteria into adjacent cells
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| − | ===Clinical infections===
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