The genus Yersinia includes 11 species, three of which are important human pathogens: Yersinia pestis, Yersinia enterocolitica, and Yersinia pseudotuberculosis . The yersinioses are zoonotic infections of domestic and wild animals; humans are considered incidental hosts that do not contribute to the natural disease cycle.
Y. enterocolitica and Y. pseudotuberculosis cause yersiniosis, a diarrheal illness. The microbiological characteristics, pathogenic determinants and laboratory isolation and characterization of Y. enterocolitica and Y. pseudotuberculosis will be reviewed here. The epidemiology, clinical manifestations and treatment of these infections are discussed separately. (See "Epidemiology of yersiniosis" and "Clinical manifestations and diagnosis of Yersinia infections".)
Y. pestis causes plague and is discussed separately. (See "Epidemiology, microbiology and pathogenesis of plague (Yersinia pestis infection)" and "Clinical manifestations, diagnosis, and treatment of plague (Yersinia pestis infection)".)
Members of the genus Yersinia are gram-negative coccobacilli; they are facultative anaerobes in the family Enterobacteriaceae . Like other Enterobacteriaceae, Y. pseudotuberculosis and Y. enterocolitica are bile tolerant and grow on MacConkey agar, they ferment glucose but not lactose, they are oxidase-negative, and reduce nitrate to nitrite.
Y. pseudotuberculosis and Y. enterocolitica are readily differentiated by biochemical tests. Y. enterocolitica ferments sucrose and Y. pseudotuberculosis does not, while Y. pseudotuberculosis ferments rhamnose and melibiose and Y. enterocolitica does not. Yersinia enterocolitica can be further subtyped into biotypes by a combination of phenotypic markers . They can also be serogrouped using antisera produced against cell surface lipopolysaccharide antigens, known classically as the O antigens [3,4]. For Y. enterocolitica, biogroup and serotype are correlated. The most common are serotype O:9 biotype 2, serotype O:3 biotype 4 and serotype O:8 biotype 1B . A similar serotyping system exists for Y. pseudotuberculosis. Both Y. enterocolitica and Y. pseudotuberculosis can be further subtyped using molecular methods such as pulsed field gel electrophoresis.