[Occurrence of virulent plasmids in strains of Yersinia obtained from various sources]

By the method of alkaline lysis the occurrence was studied of plasmid DNA in 122 strains of Yersinia. In 29 strains a single plasmid was found with characteristic growth of the organism on CRMOX (CRMOX+) medium. These features are encoded by genes located on the pYV virulence plasmid. The group of Yersinia strains possessing the virulence plasmid included 27 strains of Y. enterocolitica 0:3 isolated from clinical materials, among them 21 strains isolated from patients between January and September 1996, while the remaining two strains with the virulence plasmid belonged to Y. pseudotuberculosis antigenic group I. Following restriction analysis with the EcoRI enzyme of the virulence plasmids isolated from 27 strains of Y. enterocolitica 0:3 occurrence of only one restriction endonuclease pattern agreeing with the virulence plasmid pattern of Y. enterocolitica 0:3 strains reported in the literature was found in all strains. On the other hand, the restriction analysis of the virulence plasmids obtained from Y. enterocolitica 0:3 and Y. pseudotuberculosis I strains showed evident differences between these plasmids in the size of the particle and the restriction pattern. The plasmid size calculated on the basis of the analysis of the restriction endonuclease patterns for virulence plasmids isolated from the strains of Y. enterocolitica 0:3 and Y. pseudotuberculosis I was 71.5 thousands and 62.7 thousands of base pairs respectively, and was in the range 60-75 thousands bp (40-50 Mda) reported in the literature for virulence plasmids of Yersinia. The study showed that finding of characteristic growth of Yersinia organisms on the CRMOX medium can be useful for the detection of strains containing the pYV virulence plasmid and for the determination of their potential pathogenicity.