الفهرس 
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Abstract
ABSTRACT
Mastitis is a common and costly disease that affects dairy cattle. In the current study, the prevalence of clinical and subclinical mastitis from examination of 400 cows was 64(16%) and 36(9%) respectively. Out of 100 collected mastitic milk samples were subjected to bacteriological culturing and 49(49%) were identified as coliform bacteria on specific bacteriological media and subjected to the biochemical tests. The results revealed that E.coli 10 (20.41%), klebsiella oxytoca 4 (8.16%),klebsiella pneumoniae1(2.04%), Citrobacter 4 (8.16%), Enterobacter aerogens 2 (4.08%). Also, coliforms bacteria isolates (n=21) subjected to antibiotic sensitivity test against 10 antibiotics different groups. The result revealed high resistance to amoxicillin, cefotaxime, sulphamethaxzole/trimethoprim, and tetracycline. Meanwhile, high susceptibility for Ciprofloxaccin, Amoxicillin+Clavulinic, Streptomycin, Gentamicin, Chloramphenicol, and Colistin. In addition, out of 21 isolates of coliform bacteria strains, 12 (57.14%) isolates show multiple drug resistance against 6 different antimicrobial classes of antibiotics which are β-lactams, Aminoglycosides, Tetracyclines, quinolones, Sulfonamides, phenicols. PCR was used for detection of some virulence genes among the E.coli isolates (fimA, eaeA, sxt1, sxt2) and only the fimAgene was the only detected gene in all tested samples with 100%. Meanwhile some antibiotics resistance genes of E.coli were investigated (blaTEM, tetA, aadA, sul1, qurA) genes. The results indicated that the blaTEM gene was detected in all tested samples with 100% followed by tetA, aadA, and sul1genes with prevalence rates 40%, 30% 20% respectively. As well as the molecular characterization of Klebsiella virulence gene kfu gene detected in 1(5) tested samples with 20%. Furthermore, results of the investigation of some risk factor in the current study with prevalence of coliform mastitis revealed non-significant association with all the variables except for the type of mastitis that had significant effect on the prevalence of coliform mastitis.This study concluded that coliform bacteria were identified as major bacterial pathogens involved in bovine clinical and subclinical mastitis.