الفهرس 
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Abstract
This study aimed to assess the quality of UHT milk samples and some dairy products daily available in Mansoura University hostels and hospitals, determine the prevalence of Escherichia coli and salmonella, as well as characterization of serotypes and virulence genes of the isolated bacteria. This study was conducted on 155 random samples consisting of four different types of sterile UHT milk brands (A, B, C, D, 20 for each brand), yoghurt, processed cheese and soft cheese (25 samples of each), which were collected from the food department of Mansoura university hospitals and hostels on the same day of receiving from the company of manufacturing. The quality of collected samples was evaluated by checking the pH and titratable acidity, as well as the presence of a number of bacteria such as Escherichia coli and Salmonella through microbial isolation, serological analysis and virulence genes identification using PCR technology. Result revealed that average pH values and titratable acidity percentage in investigated samples were within the normal level, while the average of TBC and TCC exceed the acceptable limits in some samples. Three of soft cheese and two of yoghurt samples harbored E. coli while 3 of processed cheese samples were positive for Salmonella serovars (Salmonella typhimurium, Salmonella infantis and Salmonella essen). Virulence gene profiling reported the presence of eaeA and stx2 virulence genes. Further, all Salmonella isolates harbored invA and stn genes, while only Salmonella typhimurium and Salmonella infantis encoded spvC gene. Hence, the implementation of good hygiene practices together with hazard analysis, and risk-based preventive control measures are rigorously required in the process of HACCP plan to eliminate the risk of contamination that may occur during the manufacturing process to protect the consumer from food borne pathogens.