الفهرس 
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Abstract
Milk and milk products including (yoghurt, kariesh cheese and cream) are considered as one of the high nutritional quality diets consumed worldwide. They are thought to be a source of possibly injurious bacteria to human, such as pathogenic Escherichia coli that can gain access to milk via fecal contamination or via direct secretion from udder into milk.
Milk and milk products have been involved in epidemics of foodborne illness. These epidemics are mostly initiated by inappropriately pasteurized products, post pasteurization contamination, or by raw milk and raw milk products.
Avoidance of foodborne infection is a universal fear that affects all aspects of food production, including dairy one. Contamination of such products with some foodborne microorganisms as E. coli make us in necessity to use quick and precise
methods for their detection and to create proper control measures to get
red of such organisms.
The object of this work was to isolate and identify E. coli existing in milk products and to demonstrate their antibiotic sensitivity and presence of some virulence genes in these isolates that can be harmful to human, in order to be able to avoid their presence in the future.
One hundred and fifty-five (155) samples (50 yoghurt, 50 cream and 55 kariesh cheese) were collected from different markets, dairy shops and supermarkets at different localities and subjected for examination to detect the presence of E. coli. The highest prevalence (61.8%) was noted in kariesh cheese followed cream (56%), while the least prevalence was reported amongst yoghurt samples (12%).
The overall prevalence of E. coli in the examined samples of the dairy products was 43.9%.
Haemolytic activity was investigated using citrated sheep blood agar to detect the ability of the isolates to produce different types of hemolysin. Alpha hemolysis was the only type of hemolysis phenotypically detected in E. coli isolated in the present study. Alpha-hemolytic activity was reported in 16 (23.5%) out of the inspected 68 isolates (one isolate recovered from cream and 15 isolates from kariesh cheese), while the remaining isolates were non-hemolytic i.e. gamma-hemolytic.
The isolated E. coli strains were investigated for their antimicrobial susceptibility profile against different antimicrobial classes of veterinary and human significance. The result showed that E. coli isolates were sensitive to gentamicin (100%), imipenem (100) ,cefoxitin (100%) ciprofloxacin (97%), on the other hand they were resistant to ampicillin with a percentage of (11.8%), streptomycin (10.3%), Trimethoprim-sulfamethoxazole (8.8%), cefotaxime (7.4%) ,nalidixic acid (5.9%), tetracycline (4.4%) and Amoxicillin+clavulanic acid (4.4%). Moreover, multidrug resistance was noted in 10.3% of the inspected E. coli isolates.
Serological identification was done using rapid diagnostic E.coli antisera sets. The obtained results revealed the presence of 11 E. coli O groups (O25, O26, O27, O55, O78, O86, O114, O124, O125, O128, and O148) amongst the investigated 26 isolates that were selected to represent the three dairy products (yoghurt, 6; kariesh cheese, 10 and cream, 10). Serogroups O55, O114 and 125 were reported in the investigated three dairy products.
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At last, polymerase Chain Reaction (PCR) was used to detect the presence of some virulence genes in the prevalent E. coli serogroups isolated from dairy products using their specific primers. The presence of astA gene was confirmed in the ten isolates (100%) under test, while eaeA was only defined in five out of ten (50%) investigated isolates. Regarding to shiga toxins, stx1 and stx2 were only defined in one (10%) and two (20%) of the tested isolates respectively.
So, care must be taken during preparation, handling, processing, distribution and storage of milk products.