الفهرس 
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Abstract
Milk and milk products rank high among other foods and are considered as the most perfect and valuable foods for human from birth to senility. Its exceptional nutritive value is due to the high quality proteins, calcium, phosphorus, lactose, fats, minerals and vitamins. Also, milk is a very suitable medium for growth of many pathogens since raw milk and its products are subjected to contamination, either directly or indirectly from different sources. So the current study was performed to investigate the role of raw milk and some dairy products as vehicles transmitting some zoonotic bacterial pathogen to human.
A total of 200 milk and milk products (100 raw milk, 50 Kariesh cheese and 50 yogurts) samples were collected from dairy shops, street venders and supermarkets from different localities in Alexandria Province to be investigated bacteriologically for presence of some zoonotic bacterial pathogens.
1. The bacteriological examination of examined samples revealed that:
• The rates of isolation of E. coli were 18, 26 and 18 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of Salmonella species were 5, 6 and 2 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of Staph. aureus were 44, 34 and 18 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of Sheigella Spp. were 3, 4 and 0.0 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of Proteus Spp. were 12, 16 and 4 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of Citrobacter Spp. were 8, 6 and 4 % from raw milk, kariesh cheese and yoghurt samples, respectively.
• The rates of isolation of K. pneumonae were 7, 8 and 6 % from raw milk, kariesh cheese and yoghurt samples, respectively.
2. The effect of season of the year on rates of bacterial isolation from examined samples of raw milk, kariesh cheese and yoghurt was studied.
• It demonstrated higher rates of isolation in summer season than in winter season.
3. Antigenic structure of E. coli isolates recovered from different examined samples was carried out and showed that:
• E. coli isolates recovered from raw milk were O164 and O168.
• E. coli isolates recovered from kariesh cheese were O125 and O78.
• E. coli isolate recovered from yoghurt was untyple.
4. Serological identification of Salmonella isolates recovered from different examined samples was carried out and showed that:
• Salmonella serogroups recovered from examined samples were S. Enteritidis and S. Typhimurium (4 strains of S. Enteritidis were recovered from raw milk and kariesh cheese samples and one strain of S. Typhimurium was recovered from yoghurt samples).
5. Plasmid DNA profiling was evaluated as a method used for differentiation between different bacteria.
• Plasmid DNA profiling was applied on bacterial isolates of S. aureus, E. coli and Salmonella.
• Plasmid DNA can be used for differentiation between bacterial genera but not in between bacterial species. Consequently, plasmid DNA can be used for early identification of bacterial genera conditioned by knowing the size of each DNA fragment forming plasmid DNA.