Genetic variation of Yersinia enterocolitica serotype O:9 strains detected in samples from western and eastern countries.

We made use of H-serotyping, ribotyping and restriction endonuclease analysis of virulence plasmid DNA (REAP) to differentiate Yersinia enterocolitica serotype O:9 strains. A close correlation between ribotypes/REAP patterns and the geographical and chronological distribution of serotype O:9 strains was apparent. In European countries, variant clones of serotype O:9 have rapidly increased among humans and swine since the late 1980s.