الفهرس 
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Abstract
One hundred and eighty samples of milk and milk products divided as 30 samples of pasteurized milk, 90 of different samples cheese [30 of Kareish ,30 of High salt soft cheese and 30 of Tallaga cheese], 30 samples of Zabadi baladi and 30 samples of ice cream collected from super markets , farmer’s houses farmer’s houses, grocery stores and and dairy shops. The samples were enriched in modified vancomycin- trypticase soy broth and incubated at 37°C for 24 h. then inoculated into Sorbitol MacConkey agar plates and incubated at 37°C for 24 h. Suspected E. coli non O157 colonies were bright pink and sorbitol positive.Various biochemical tests were done for the confirmation of E. coli non-O157. Serodiagnosis of E. coli non-O157 has been done using slide agglutination test. Toxigenic E. coli non-O157 isolates were detected using PCR assay.
Results postulated that the detection rate of non O157 using biochemical technique was 20% in pasteurized milk, 63.33% in Kareish cheese, 20% in High salt soft cheese, 33.33% in Tallaga cheese, 30% in the Zabadi baladi and 10% in Ice cream samples. 10 different serotypes of E. coli non O157 distributed as following O1 (3.33%), O18 (1.11%), O20 (0.56%), O25 (0.56%), O26 (2.78%), O44 (1.11%), O125 (0.56%), O126 (0.56%), O127 (0.56%), O158 (0.56%) and untyped E. coli (12.22%). Regarding PCR results, serotypes group (O1) was positive for Stx2gene, (O1and O20) were positive for both Stx2 and hly genes, one serotype group O25 was positive for eaeA gene, 4 serotype groups (O1, O18, O26, O44) were positive for hly gene while no detection for Stx1and STa genes.Recent studies described the effect of lactoferrin on release and bioactivity of Shiga toxin from different E. coli O157:H7 strains but no advanced preclinical trials or applications on its effect on E. coli non 0157 have been reported to date. So, this work adopted to study the effect of lactoferrin on growth of some isolated E. coli non O157 in Lauria broth and in pasteurized milk.
Ten strains of E. coli carry shiga toxin genes [O18, O20, O25, O44 (1 strain each), O26 (2 strains) and O1 (4 strains)] were used. These strains were previously isolated from milk and milk products samples and differentiated serologically and by using PCR technique. Different concentrations of lactoferrin (zero, 0.5, 1.0, 5.0, 10 and 20 mg/ml) were used. Based on our results, LF has varied inhibition activity on E. coli non O157 growth in Lauria broth. Significant decrease observed on growth of E. coli O1 and E. coli O44. Higher concentrations of lactoferrin cause significant decrease in E. coli O25 and E. coli O26 growth. On the other hand, lactoferrin has no significant effect on E. coli O18 and E. coli O20 growth. Regarding its effect on pasteurized milk, significant decrease in the count of E.coli O1 and O26 at the concentrations of 10 and 20 mg/ml lactoferrin were noticed. So, more studies needed on the effect of lactoferrin on the viability of E. coli non O157 regarding different dairy products.