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===Overview===
*Cause [[Intestine Pathogens - Pathology|intestinal disease]] in animals and are important zoonoses
*10 species of which [[Yersinia pestis|''Y. pestis'']], [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis]] and [[Yersinia enterocolitica|''Y. enterocolitica'']] are pathogenic to animals and humans; [[Yersinia pestis|''Y. pestis'']] is the most pathogenic
*Rodents provide a reservoir of [[Yersinia pestis|''Y. pestis'']], which is the cause of human plague; fleas transmit the infection to other animals and humans
*[[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] and [[Yersinia enterocolitica|''Y. enterocolitica'']] reside in the intestine of domestic and wild animals and birds
*Birds may cause mechanical transfer of the organisms
===Characteristics===
*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
===Pathogenesis===
*[[Yersinia enterocolitica|''Y. enterocolitica'']] and [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] enter the intestinal mucosa via M cells of the Peyer's patches
*Engulfed by macrphages in the mucosa
*All three invasive species are facultative intracellular organisms and grow inside macrophages
*Plasmid and chromosomal-encoded virulence factors required for survival and multiplication in macrophages
*Survive in phagolysosomes and do not interfere with degranulation or lysosomal fusion
*Resistant to macrophage killing mechanisms
*Antiphagocytic proteins secreted by the organisms interfere with host [[Neutrophils - WikiBlood|neutrophils]]
*[[Yersinia pestis|''Y. pestis'']] is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity
*Transport within macrophages to mesenteric lymph nodes
*Replication in lymph nodes and development of necrotic lesions, with neutrophil invasion
*The bacteria destroy the macrophages causing septicaemia
===Clinical infections===
*''[[Yersinia pestis]]''
*''[[Yersinia pseudotuberculosis]]''
*''[[Yersinia enterocolitica]]''
===Diagnosis===
*''Yersinia'' species grow on blood agar and MacConkey agar at room temperature.
*''Y. pseudotuberculosis'' and ''Y. enerocolica'' are motile, unlike ''Y. pestis''
*Biochemical tests to identify particular species
*Specific fluorescent antibody staining of lymph node aspirates to identify ''Y. pestis''
===Control===
*Control ''Y. pestis'' by controlling rodent population and flea control of cats
*Control of other ''Yersinia'' species difficult due to their ubiquity
===Treatment===
*Euthanase or isolate animals suspected of ''Y. pestis'' infection; Streptomycin, doxycycline, gentamicin or chloramphinol
*Long-acting tetracyclines, trimethoprim-sulphonamides, aminoglycosides and chloramphicol effective against ''Y. pseudotuberculosis'' and ''Y. enterocolica''
[[Category:Enterobacteriaceae]]
[[Category:Enterobacteriaceae]]