Isolation of Yersinia enterocolitica and related species from porcine samples obtained from an abattoir.

Swabs of swine carcasses and samples of porcine tongue and trim obtained from an abattoir were examined for the presence of Yersinia enterocolitica and related species (Y. intermedia, Y. kristensenii and Y. frederiksenii). Three enrichment media (phosphate buffered saline, sorbitol-bile salts-phosphate buffered saline, and a modified Rappaport's broth) were compared at 4 degrees C for their efficiency of recovery of Y. enterocolitica and related species. Two secondary enrichment procedures (post-enrichment in modified Rappaport's broth for 2 d at 25 degrees C and treatment with 0.5% KOH in 0.5% NaC1) also were evaluated. The porcine isolates were characterized by biochemical and serological examination, speciation, and biotyping. Eight of 43 samples were positive for Y. enterocolitica and related species. The combination of incubation in sorbitol-bile salts-phosphate buffered saline for 21 d at 4 degrees C followed by post-enrichment in modified Rappaport's broth yielded maximum number of isolates. All isolates, except one, were avirulent as determined by autoagglutination, calcium dependence at 37 degrees C, and HeLa cell invasiveness tests.