Detection of a novel repeated sequence useful for epidemiological typing of pathogenic Yersinia enterocolitica

Strains (n=203) of Yersinia species were used in genotyping and PCR experiments in order to evaluate the genotyping potential of the YeO:3RS probe. This probe comprises a 12.5 kb genomic fragment of the Y. enterocolitica O:3 lipopolysaccharide O-antigen gene cluster cloned into plasmid pBR322. The genotyping potential of YeO:3RS was shown to reside in the region upstream of the O-antigen gene cluster, i.e., in the first 1.65 kb of the cloned genomic fragment that contains a repeated sequence (RS) present in multiple copies in the genome. In genotyping, the YeO:3RS probe was hybridised to DNA of Yersinia enterocolitica isolates (n=112) from humans, animals and food, along with strains of other Yersinia species (n=5) and Salmonella enterica strains (n=3). The YeO:3RS probe efficiently detected and subtyped all European pathogenic Yersinia enterocolitica isolates of the serobiotypes O:3/4, O:9/2 and O:5,27/2 studied (n=87), whereas it hybridised only weakly or not at all with the other strains. Within Yersinia enterocolitica serobiotype O:3/4 strains, YeO:3RS genotyping was as discriminatory as genotyping by pulsed-field gel electrophoresis (PFGE) of XbaI-NotI digested genomic DNA. When these two methods were combined, YeO:3RS genotyping divided both of the two predominant PFGE types into six subtypes, thus increasing the discrimination. In PCR screening of additional 86 Yersinia strains, the 1.65 kb region was detected in European pathogenic serotypes O:1 and O:2 in addition to serotypes O:3, O:5,27 and O:9, indicating that it can be exploited in detecting and typing of European pathogenic serotypes in general.