A novel insertion sequence element, ISYen2, as an epidemiological marker for weakly pathogenic bioserotypes of Yersinia enterocolitica

The structure and distribution of ISYen2, a new Yersinia enterocolitica insertion sequence element, were investigated. ISYen2 is related to IS elements of the IS21 family and is present in two isoforms in Y. enterocolitica serotype O:3. Analysis of all copies of both isoforms, ISYen2A and ISYen2B, by PCR and sequencing indicated that they are not flanked by direct repeats which are typical of the IS21 family of repetitive elements. ISYen2 is present in multiple copies in Y. enterocolitica O:3 and O:9 and in a single copy in Y. enterocolitica O:1 and O:2 serotypes. The probe for ISYen2 efficiently detected all weakly pathogenic Y. enterocolitica bioserotypes investigated, whereas it did not hybridize with other strains. This indicates that ISYen2 can serve as an additional tool for Y. enterocolitica differentiation and epidemiological studies. Distribution of the different groups of IS elements in two Y. enterocolitica pathotypes is in favor of the parallel evolution of American and European Y. enterocolitica strains.