Different genotypes of Yersinia enterocolitica 4/O:3 strains widely distributed in butcher shops in the Munich area

Abstract

The distribution of Yersinia spp. in butcher shops in the Munich area was studied. The isolates recovered were then characterised with pulsed-field gel electrophoresis (PFGE) to identify possible contamination routes. A total of 298 samples were collected from eight small butcher shops between June and August in 2001. Of these, 113 were surface samples from carcasses, offal and raw pork products, and 185 were environmental surface samples from tools, equipment and processing areas. The samples were studied with direct plating, overnight enrichment in nonselective broth and selective enrichment in two different enrichment broths. The Yersinia isolates recovered were characterised with PFGE using NotI, ApaI and XhoI DNA restriction enzymes. Yersinia was recovered from all eight butcher shops, and pathogenic Yersinia enterocolitica 4/O:3 was present in six shops. The occurrence of this pathogen on raw pork products varied from 8% to 25%. Pathogenic Y. enterocolitica 4/O:3 was isolated from two environmental samples: a worktable and a chain glove. Most (18/24) of the Yersinia-positive samples were found already after direct plating. Forty-nine Yersinia isolates from 24 samples were studied with PFGE. Twelve genotypes (I–XII) were obtained among Y. enterocolitica 4/O:3 when 33 isolates from 16 samples were characterised with NotI, ApaI and XhoI enzymes. The genotypes of Y. enterocolitica 4/O:3 strains differed among butcher shops. In most (5/6) shops, more than one genotype was found, indicating different contamination sources. In conclusion, raw pork products from butcher shops are frequently contaminated with different genotypes of pathogenic Y. enterocolitica 4/O:3, thus serving as an important transmission vehicle from butcher shops to humans.