Resumo

Introduction: Yersinia pseudotuberculosis is one of the major pathogenic species of the genus Yersinia and is capable of infecting a broad range of animals, including humans. This bacterium causes enteric disease with both sporadic and epidemic patterns. Molecular typing studies have been used successfully for the genotypic characterization of Y. pseudotuberculosis strains isolated worldwide. In this work, the pulsed-field gel electrophoresis (PFGE) technique was used to access the molecular diversity of Y. pseudotuberculosis strains isolated in Brazil for 27 years. Materials and methods: A total of 60 Y. pseudotuberculosis strains belonging to bio-serogroups 1/O:1a and 2/O:3 collected from healthy and sick animals from sporadic cases and outbreaks of hemorrhagic gastroenteritis among livestock in Brazil from 1982 to 2009 were studied. In the PFGE assay, the plugs were digested with 40U of XbaI overnight. Macrorestriction fragments were resolved in a CHEF-DR III apparatus with an electric field of 6V/cm and angle of 120°. The pulse times were increased from 1 to 10s over 29h. Only bands between 48.5 and 194 Kb were analyzed. The relatedness among the PFGE profiles was determined with the software package BioNumerics 7.0. A similarity dendrogram was constructed using the UPGMA method with the Dice similarity coefficient. Results: The fingerprint analysis based on the XbaI-PFGE assay grouped the 60 Y. pseudotuberculosis strains into two major clusters. One cluster (A) was composed by three undistinguishable strains belonging to the 1/O:1a bio-serogroup. The other cluster (B) was composed by 57 strains belonging to the 2/O:3 bio-serogroup with 90.2% of similarity. Strains belonging to the A and B clusters had a genetic similarity of 80.1%. No correlation among the Y. pseudotuberculosis strains isolated in Brazil was observed according their geographical origin, host and place and year of isolation. Conclusion: The Y. pseudotuberculosis strains studied showed to be very similar. The PFGE assay was able to establish clonal patterns among the Y. pseudotuberculosis strains isolated from livestock in Brazil. The grouping of the Y. pseudotuberculosis strains isolated in Brazil into two main clusters according to their bio-serogroups determined by the PFGE assay suggests that the Brazilian livestock harbor two distinct subpopulations of Y. pseudotuberculosis.