الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
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Abstract
E.coli is one of the most frequently isolated pathogens from both clinical and chronic mastitis infection, it was more sever than the other bacterial causes and it tended to be more severe in early lactation and during the housing period, resulting in inflammation that ranges from sub acute to per-acute. Necrosis of the mammary epithelium occurs during severe, naturally occurring clinical E.coli mastitis. In moderate cases of E. coli mastitis, there is minimal alveolar tissue damage.This study is carried out to investigate epidemiological and bacteriological aspects of E.coli mastitis in cattle through:1-Isolation and serotyping of E.coli associated with mastitis in cattle 2- characterization of some virulence factors present in E.coli isolates from bovine mastitis 3- Determination of the antimicrobial susceptibility of E.coli isolated from bovine mastitis 4- Investigation the association between virulence factors and antimicrobial resistance of the isolates with clinical signs of E.coli mastitis Our study revealed that the percentage of E.coli mastitis in cows (in farms and individual animals) was 20% and we found that the mostly affected quarters were the hind quarters (40.857%) while the fore quarters were the least (22.427%). The percentage of E.coli mastitis in buffaloes was 14.5% and also the most affected quarters were the hind (12.5%) and the least were the fore quarters (5.83%).The subclinical cases tested by CMT then bacteriologically for detection of E.coli cases and the percent of E.coli cases was 6.8% in both cows and buffaloes. The most affected age by E.coli mastitis in cows was over 7 years (25%)and the least affected age was 3-4 years age (1.8%) and in buffaloes also the highest incidence was at age over 7 years (11.76%) and the least incidence at age of 3-4 years (0%). Most cases of E.coli mastitis were reported in early lactation (18.18%) and the lowest cases reported at 7-9 moths (at late lactation stage (6.25%). The most isolated bacteria mixed with E.coli were staph. (36%) then streptococcus (24%) and Corynebacterium (10%) The clinical signs of E.coli mastitis differ greatly from severe clinical signs (severe inflammation in the udder hotness, swelling, tenderness and rise of animal temperature) to mild with only local signs in the udder. Serotyping of E.coli isolates revealed that O55 (30%), O111 (15%), O124 (15%), O119 (10%), O114 (10%), O26 (5%), O157 (10%) and O44 (5%). That’s showing that O55, O111 and O124 the most serotypes causing mastitis. PCR identification of TraT gene revealed that this gene gives positive reaction at 307 bp. and eaeA gene gives positive reaction at 384 bp. The antimicrobial sensitivity was carried out on several types of antibiotics using the disc diffusion method. The results indicated that the most effective antibiotics were lincospectine (56.6%), danofloxacin (56.6%), marbofloxacin (50%), enrofloxacin (40%) and ceftifure (40%), while the lowest effective antibiotics were oxytetracycline and ampicillin.