Isolation and identification of Yersinia pseudotuberculosis and Yersinia enterocolitica from cow raw milk in Tehran

Aims and background: Yersinia is a cocobacilliary gram-negative bacteria which can cause yersiniosis in all age groups. This study was carried out to investigate the presence of Yersinia pseudotuberculosis and Yersinia enterocolitica in raw milk of livestock farms in Tehran. Materials and methods: Three hundred and sixty raw milk samples were collected from livestock farms in Tehran during 6 months. Y. pseudotuberculosis and Y. enterocolitica were isolated and identified according to the FDA guidelines. After treatment with low temperature (10°C for 10 days) and alkaline treatment (using KOH), the samples were cultured in the selective medium named CIN agar at 25°C. After incubation, colonies similar to the bull eye were chosen and characterized using phenotypic tests and ultimately confirmed by the API-20E strip test (Biomerieux, France) and detection of ail and inv genes by PCR. Serotyping and bio typing tests carried out on Y. enterocolitica isolates. Results: Of 360 samples, a total of four isolates were identified as Yersinia species, including three Y. enterocolitica and one Y. pseudotuberculosis. Conclusion: Due to the presence of Y. pseudotuberculosis and Y. enterocolitica in raw milk, it is suggested that the food and drug control laboratories, milk factories and other researchers pay more attention to these bacteria.