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| <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> | | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> |
| <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> | | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> |
| + | |
| + | ===Overview=== |
| + | |
| + | *6 species |
| + | *Saprophytes in soil |
| + | *''L. monocytogenes'' and ''L. ivanovii'' are pathogens |
| + | *Carried by sheep and goats and shed in faeces and milk especially during stress |
| + | *Can cause septicaemia, encephalitis and abortion |
| + | |
| + | |
| + | ===Characteristics=== |
| + | |
| + | *Small Gram negative rods |
| + | *Catalase positive, oxidase negative |
| + | *Motile |
| + | *Facultative anaerobes |
| + | *''L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures |
| + | *''L. ivanovii produces strong haemolytic zone |
| + | *Small, smooth, transparent colonies after 24 hours incubation |
| + | |
| + | |
| + | ===Pathogenesis and pathogenicity=== |
| + | |
| + | *Infection by ingestion of contaminated feed |
| + | *Bacteria penetrate M cells in intestinal Peyer's patches |
| + | *Spread to tissues via blood and lymph |
| + | *Transplacental transmission in pregnant animals |
| + | *Bacteria may gain entry via breaks in oral or nasal mucosa, migrate in cranial nerves to cause neural signs |