Molecular characterization of Yersinia strains isolated from human and environmental sources

Thirty-seven strains of Yersinia isolated from human and environmental sources were investigated for virulence and molecular characteristics. Clinical isolates of Y. enterocolitica serotypes 0:3 and 0:9, harbouring the 45 MDa virulence plasmid were Ca++ dependent and responded positively to the CV-binding assay. The environmental Y. kristensenii strain, although harbouring a 45 MDa plasmid proved to be negative for both assays. All the environmental strains showed pyrazinamidase activity, while isolates from human sources proved negative. Two different plasmid profiles were disclosed: one Y. enterocolitica strain (serotype 0:7, 8) showed one plasmid of 67 MDa and one plasmid of 1.5 MDa. Eleven human isolates of Y. enterocolitica and one environmental strain of Y. krinstensenii showed only one plasmid of 45 MDa. Restriction endonuclease analysis of the 45 MDa plasmids supported the hypothesis that the environmental Y. krinstensenii plasmid is unrelated to the family of homologous virulence plasmids of Y. enterocolitica.