Comparison of Two Enrichment Protocols for the Detection of Yersinia in Slaughtered Pigs and Pork Products

Abstract

Two enrichment methods were evaluated in the course of a study to determine the occurrence of Yersinia enterocolitica in slaughtered pigs and pork products. Eighty Yersinia strains belonging to one of four species were recovered. Of the 67 strains of Y. enterocolitica encountered, 48 belonged to known pathogenic bioserotypes. The enrichment medium incorporating irgasan, ticarcillin, and potassium chlorate (ITC) was found to be superior to the two-step enrichment method (YER/BOS) for isolation of pathogenic Y. enterocolitica from throat swabs. When pork products were examined using the two methods, YER/BOS was by far superior for recovery of yersiniae, although all strains isolated by this method belonged to nonpathogenic bioserotypes and Y. enterocolitica-like organisms. Conversely, ITC enrichment recovered fewer strains but most were pathogenic bioserotypes. Thus, swine can serve as a reservoir of virulent Y. enterocolitica in Saskatchewan, and ITC enrichment is recommended for the isolation of these strains.