Yersinia enterocolitica and Shigella spp. in pasteurized milk

Abstract

In this study, it was planned to investigate the presence and serotypes of Yersinia enterocolitica (Y. enterocolitica) in various pasteurized milk samples, collected from retail markets in Kırıkkale region, using classical isolation and identification. Pasteurized milk samples were taken for isolation in the study; aseptically, 25 g of the sample was added to 225 ml of Peptone Sorbitol Bile Buyyon (PSBB). 30 s were homogenized and incubated at 10 ° C for 10 days. On day 10, the enrichment water was removed from the incubator and thoroughly mixed. From the enrichment water, 0.1 ml in 0.5% saline was transferred to 0.5% KOH and stirred for 2-3 seconds. Decouple one loop to the Mac Conkey plate and one loop to the CIN plate successively. After 1 day of incubation, the CIN plates were examined. Small (1-2 mm in diameter) colonies with a sharp-edged dark red center, the entire edge of which is surrounded by a clear colorless zone, were selected for identification. Colonies showing characteristic features after incubation were identified by a rapid identification system (BBL, Crystal). Y. enterocolitica could not be isolated in 100 of the pasteurized milk samples that were examined, but yeast was detected in 6 milk samples and Shigella spp. were detected in one of the samples. The reason why Yersinia spp. could not be isolated in our study, might be that the pasteurization process prevented the reproduction of Yersinia spp., but did not prevent the growth of Shigella spp. It is thought that working with a higher number of samples may increase the isolation rate, and Y. enterocolitica and Shigella spp., which are important sources of infection, should be examined in pasteurized milk.