Pathogenicity of Yersinia enterocolitica biotype 1A.

Yersinia enterocolitica strains of biotype 1A lack the known virulence determinants of strains in other categories, including the Yersinia virulence plasmid (pYV), and several chromosomal markers of pathogenicity. For this reason, and also because Y. enterocolitica strains of biotype 1A are frequently isolated from the environment or asymptomatic individuals, these bacteria are often assumed to be avirulent. On the other hand, there is a considerable body of clinical, epidemiological and experimental evidence to indicate that at least some strains of Y. enterocolitica biotype 1A are able to cause gastrointestinal symptoms which resemble those caused by pYV-bearing strains. The availability of a number of experimental systems, including cell culture and animal models of infection, provides an opportunity to identify and characterise the essential virulence determinants of biotype 1A strains.