الفهرس 
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Abstract
This study included 200 Samples table eggs, cheeses ( Ras and Talaga Low Salt Cheese,25 sample each) , milk pudding and Creme Caramel Custard (50 samples each) will be collected from different regions in Mansoura city, El-Dakhlia, Egypt. In this study Salmonella, E. coli and B. cereus were isolated followed by biochemical reaction, molecular identification, antimicrobial sensitivity test, Also, we determined the prevalence of Salmonella ,E. coli and B. cereus in the previous mentioned samples. Salmonella is still a major concern for table eggs and dairy industry due to public health hazards. eggs and dairy products are the most important foods implicated in Salmonella outbreaks. We recovered Salmonella from examined samples using XLD and Ramach agar as a selective media. The prevalence of Salmonella in table eggs, Talaga Low Salt Cheese and RAS cheese was 24%, 40% and 20% respectively. While the numbers of Salmonella isolates in our study were 10 isolates recovered from table eggs and 13 isolates recovered from Talaga Low Salt Cheese while12 isolates recovered from Ras Cheese. All Salmonella isolates were confirmed by biochemical tests, serological analysis and PCR. The results of salmonella serological analysis revealed 5 various serotypes. 11 strains belonged to S. Enteridis, 7 strains belong to S. Typhimurium, 6 strains belonged to S. Infantis, 4 strains belonged to S. Heidelberg and Two strain belonged to S. Tsevie. Antibiotic susceptibility test of salmonella strains showed that 100% of isolates were resistant to streptomycin and erythromycin. About 60% of isolates were resistant to nalidixic acid and sulphamethoxazol, 80% of isolates was resistant for each oxytetracycline. Nearly 60-80% of isolates were resistant to cephalothin, cholarmphenicol,amikacin and kanamycin, cefotaxim. Less than 50% of isolates were resistance to kanamycin, neomycin, gentamicin, and ciprofoxacin. PCR was used for detection of some virulent genes for Salmonella as invA, avra and stn genes. Escherichia coli lives in the intestines of animal and human and its nonpathogenic but under adverse stress conditions it becomes pathogenic for human or animals and it considers a good indicator for un hygienic measures. We used sorbitol macConkey agar media supplemented with cefixime and potassium tellurite for isolation of E. coli. The prevalence of E. coli O157 in table eggs, Talaga Low Salt Cheese and RAS cheese was 6%, 28%, and 16%, respectively. While the numbers of E. coli O157 isolates were 6, 12, 5 in table eggs, Talaga Low Salt Cheese and RAS cheese, respectively. That confirmed by serological and molecular analysis. Antimicrobial susceptibility of isolated E. coli strains revealed that 75% or above of isolates were resistant to erythromycin, streptomycin, nalidixaic acid, sulphamethooxazol and cefotaxim. The resistance of isolates to neomycin, chloramphenicol, and cephalothin were 70%, 60% and 60%, respectively. Less than 50% of isolates were resistance to other tested antibiotics as oxytetracycline (40%), amikacin (30%), ciprofloxacin (20%), kanamycin (20%) while gentamicin and Colistin were (0%). We also used PCR for determination of some virulent genes as eaeA, stx1, stx2 and rfbE genes. Our results illustrated the priority of isolates for stx1 than stx2 in all STEC populations. where all isolates harbored stx2 genes. One hundred samples of dairy desserts (milk pudding and Creme Caramel Custard, 50 of each) were examined for detection, enumeration and molecular examination of B. cereus. The results showed that all samples were positive for Bacillus species . The prevalence of B. cereus was 58% in milk pudding samples While 74% of Crème Caramel custard samples were contaminated with B. cereus It could be concluded that other bacillus species were isolated as showed; Bacillus subtilis in 70% from examined milk pudding samples, 84 % Creme Caramel Custard samples. B. pumilus could be detected in 30% and 58% from milk pudding and Creme Caramel Custard; respectively. B. lichenformis presented in 18% and 24% from milk pudding and Creme Caramel Custard, respectively. Twenty B. cereus isolates confirmed biochemically obtained from the examined dairy desserts were molecularly scanned for groEL gene which is the specific B. cereus group gene, 18 (90%) of examined isolates found to harbor it. Eighteen isolates which confirmed to be B. cereus were examined for the presence of the potential toxin genes known to be responsible for virulence B. cereus. Emetic toxin ces gene could be detected in 25% of the isolates. Diarrheal toxin genes Nhe, Hbl and CytK could be detected in 100%, 77.8 %, 100%, respectively of isolates obtained from examined dairy desserts. Antibiotic susceptibility test of B. Cereus strains showed that 100% of isolates were senstive to streptomycin and erythromycin, cephalothin, cholarmphenicol, amikacin, kanamycin, gentamicin, ciprofloxacin and cefotaxim. While 90% of isolates were resistant to novobiocin and Less than 30% of isolates were resistance to oxytetracycline, neomycin and sulphamethoxazal.