[Presence of Yersinia enterocolitica in raw cow's milk]

Studied were a total of 286 samples of raw milk from 12 dairy farms for the presence of Yersinia enterocolitica. Various methods and nutrient media were tested for the successful isolation of this organism. It was found that 11.89 per cent, on an average, of the investigated samples contained Y. enterocolitica. The positive samples on the individual farms varied from 0 to 33.33 per cent. Best results were obtained with the use of the phosphate buffer physiologic saline and Rappaport's modified broth at two-step enrichment. The reseeding on MacConkey and Endo agar as well as the treatment of the enriched media with weak solutions of KOH made it feasible to isolate and identify the organisms of Y. enterocolitica. It was also established that the Y. enterocolitica strains isolated from raw cow milk did not refer to the European serotypes 0:3 and 0:9 that were pathogenic for humans. Biochemically, the isolated ones were found to belong to the newly suggested Yersinia frederiksenii and Yersinia intermedia.