الفهرس 
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Abstract
One hundred and sixty samples of raw milk (40) and milk products including small scale ice cream (40), Kareish cheese (40) and Domiati cheese (40) were collected randomly from supermarkets, dairy farms, dairy shops and street vendors, in Assiut city. The samples were examined for the existance of Yersinia species using selective CIN (Cefsulodin-Irgasan-Novobiocin) agar plates.
The recorded data revealed that when phosphate buffered saline (PBS) was used as an enrichment broth supplemented with novobiocin and cefsulodin, and CIN (Cefsulodin-Irgasan-Novobiocin) agar as a selective culture medium, the incidence of Yersinia species 24 (60%) were isolated from raw milk samples, 8 (20%) from small scale ice cream and one (2.5%) sample from Kareish cheese, on the other side, the organism could not be detected from Domiati cheese. It is noticeable that the highest isolation rate was in raw milk, followed by ice cream and Kareish cheese.
By using biochemical tests for differentiation between Yersinia species, resulting the identification of Yersinia isolates on CIN medium; Yersinia enterocolitica was detected in 15 (37.5%) samples of raw milk, 3 (7.5%) of small scale ice cream and 1 (2.5%) of Kareish cheese. Yersinia pseudotuberculosis was only detected in raw milk samples (7.5%), furthermore, Yersinia pestis and Yersinia intermedia were found in 3 (7.5%) , 3 (7.5%) , 4 (10%) , 1 (2.5%) of raw milk and small scale ice cream samples, respectively.
Polymerase Chain Reaction (PCR) via detection of virulent ail gene was performed on 19 isolates of Yersinia enterocolitica previously identified by biochemical tests, 4 of them were confirmed to be pathogenic Yersinia detected in raw milk strains only. virulent ail gene not found in other Yersinia enterocolitica strains of milk products.
The public health importance and the suggestive sanitary measures were also discussed to protect consumers from the infection with Yersinia.