Molecular typing of Yersinia pseudotuberculosis by using an IS200-like element

The IS200-like insertion sequence (IS) is a 708-bp element recently found in Yersinia pestis. Its nucleotide sequence is 85% identical to that of IS200 recovered in most Salmonella enterica isolates. It is also present in multiple copies in Y. pseudotuberculosis. In contrast, this IS is found in some (biotype 1B strains) but not other Y. enterocolitica strains and is absent in the nonpathogenic yersiniae: Y. frederiksenii, Y. kristensenii, Y. intermedia, Y. bercovieri, and Y. mollaretii. The number and locations of the ISs in the Y. pseudotuberculosis genome vary among strains, resulting in a high degree of polymorphism, but IS fingerprints are stable after multiple subcultures of clinical isolates. The discriminative power of IS typing is better than that of ribotyping and almost as good as that of the time-consuming method of pulsotyping. Overall, IS200-like is a useful molecular marker in determining the epidemiology of Y. pseudotuberculosis infections.