Variations in the 16S rRNA gene sequence of Yersinia enterocolitica isolates influence the specificity of molecular identification systems

Four identification systems were used to type Yersinia enterocolitica strai n Y11 and Yersinia enterocolitica sensu stricto(T). Two systems based on bi ochemical reaction patterns identified both strains as Yersinia enterocolit ica. Two molecular assays targeting the 16S rRNA gene failed to identify ei ther strain Y11 or the type strain. Therefore, both strains were typed by t he classical taxonomical approach requiring a determination of the overall base composition and the base sequence similarity using hybridization. Agai n both strains were classified as Yersinia enterocolitica isolates. Consequ ently, the sequences of the 16S rRNA gene of both strains were determined a nd compared. The strains differed in a region where nucleotide changes betw een species of the genus Yersinia had been described earlier. These differe nces may explain the failure of the molecular assays to identify the strain s. They also demonstrate an independent evolution of the 16S rRNA genes in the species Yersinia enterocolitica sensu stricto suggesting an amendment t o the nomenclature to be used in the future.