Abstract
The aim of this study was to investigate the incidence of yersinia species specifically Y. enterocolitica and Y. pseudotuberculosis as a food borne pathogens in milk samples of different animal species. Moreover, the virulence and antibacterial susceptibility of the isolated yersinia spp. were also investigated. Therefore, 284 milk samples were collected from different animal species including cows ]bulk tank milk (BTM) and individual animals [, buffaloes, goats and she-camels. Based on culture method, 110 presumptive yersinia isolates were recovered in an overall percentage of 38.7% while based on PCR, only 87 out of 110 isolates were confirmed to be yersinia spp. Out of those 87 PCR confirmed strains, 39, 27, 13, 3 and 5 isolates were identified biochemically to be Y. enterocolitica, Y. intermedia, Y. frederiksenii, Y. Kristensenii and Y. pseudotuberculosis, respectively. Based on PCR results, 32, 5 and 50 isolates were identified to be Y. enterocolitica , Y. pseudotuberculosis and other yersinia spp, respectively. Conventionally, 35 strains were pathogenic while the rest of 87 strains (52) were non pathogenic which declared the high incidence rate of virulent strains. The ail gene was positive in 11/32 (34.4%) Y. enterocolitica strains and 3/50 (6%) of the other yersinia spp. Inv gene was positive only in 2/5 (40%) Y. pseudotuberculosis strains. Likewise, 25% of the tested Y. enterocolitica strains showed multi-drug resistant to all used antibacterial agents. In conclusion, these results declared that the applied PCR-based approach can support the conventional methods used for isolation and identification of yersinia spp. in milk samples. Furthermore, results of this study highlights the role of milk as a transmission vehicle of potentially pathogenic Y. enterocolitica and Y. pseudotuberculosis strains, with consequent risks for consumer’s health via the consumption of raw and unpasteurized milk.

Key words: Y. enterocolitica; Y. pseudotuberculosis; milk; isolation; identification; PCR; virulence; antibacterial susceptibility