Phenotypic and genotypic presence of the Yersinia virulence plasmid do not affect the production of enterotoxin YstA by Yersinia enterocolitica strains.

The aim of the study was to determine whether the presence of the Yersinia virulence plasmid could affect the production of enterotoxin YstA by Y. enterocolitica strains isolated from pigs which are the main source of infection for humans. The phenotypic features characteristic for the Yersinia virulence plasmid were detected on CRMOX agar in 8 out of 12 strains producing enterotoxin YstA, in 5 out of 12 doubtful strains, and in 11 out of 12 strains not producing YstA. Autoagglutination ability was detected in all 12 Y. enterocolitica strains that were positive in the suckling mice bioassay, in 11 doubtful strains and 10 negative strains. CRMOX+ colonies were generally ystA, myfA, virF and yadA positive, while CRMOX- colonies were only ystA and myfA positive. The amplicons of yadA were not detected in 2 (8.3%) out of 24 CRMOX+ and virF positive strains. The results of this study indicate that the presence of pYV does not affect the enterotoxin-producing ability of Y. enterocolitica strains.