USE OF A SINGLE PROCEDURE FOR SELECTIVE ENRICHMENT, ISOLATION, AND IDENTIFICATION OF PLASMID-BEARING VIRULENT YERSINIA-ENTEROCOLITICA OF VARIOUS SEROTYPES FROM PORK SAMPLES

Many selective enrichment methods for the isolation of Yersinia entero colitica from foods have been described, However, no single isolation procedure has been described for the recovery and identification of va rious plasmid-bearing serotypes. A single improved procedure for selec tive enrichment, isolation, identification, and maintenance of plasmid -bearing virulent serotypes of Y. enterocolitica from pork samples was developed, Enrichment at 12 degrees C in Trypticase soy broth contain ing yeast extract, bile salts, and Irgasan was found to be an efficien t medium for the recovery of plasmid-bearing virulent strains of Y. en terocolitica representing O:3; O:8; O:TACOMA; O:5, O:27; and O:13 sero types, MacConkey agar proved to be a reliable medium for the isolation of presumptive colonies, which were subsequently confirmed as plasmid -bearing virulent strains by Congo red binding and low calcium respons e. Further confirmation by multiplex PCR employed primers directed at the chromosomal ail and plasmid-borne virF genes, which are present on ly in pathogenic strains, The method was applied to pig slaughterhouse samples and was effective in isolating plasmid-bearing virulent strai ns of Y. enterocolitica from naturally contaminated porcine tongues. S trains isolated from ground pork and tongue expressed plasmid-associat ed phenotypes and mouse pathogenicity.