Yersinia

Cause disease in animals and are important zoonoses
10 species of which Yersinia pestis, Yersinia pseudotuberculosis amd Yersinia enterocolitica are pathogenic to animals and humnans
Rodents provide a reservoir of Yersinia pestis, which is the cause of human plague; fleas transmit the infection to other animals and humans
Yersinia pseudotuberculosis and enterocolitica reside in the intestine of domestic and wild animals and birds
Birds may cause mechanical transfer of the organisms

Enterobacteria, but grow more slowly and at lower temperatures than other enterobacteria
Gram negative, non-spore forming, facultative anaerobes - rods or colibacilli
Non-lactose fermentors
Facultative intracellular pathogens
Show bipolar staining in Giemsa-stained smears from animal tissue
Pathogenic strains identified by serotyping and biotyping

Invasive Yersinia grow inside macrophages
Survive in phagolysosomes and do not interfere with degranulation or lysosomal fusion
Resistant to macrophage killing mechanisms
The bacteria destroy macrophages in lymph nodes, liver and spleen, causing septicaemia

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