الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Mastitis is a serious problem in dairy farms, not only for the associated economic losses, but also, and importantly, for the health hazards of zoonotic diseases in which milk acts as the vehicle of infection. Results showed that the overall incidence of mastitis in the examined dairy cows was high (75%), with a nearly equal incidence of subclinical (38.23%) and clinical (36.76%) mastitis. Among the subclinically mastitic cases the rate of involvement of one, two, three and four quarters was 21.15%, 25%, 36.53% and 17.3%, respectively, while among the clinically mastitic cases, the rate of involvement of one, two, three and four quarters was 48%, 42%, 24% and 20%, respectively. Bacteriological examination of 272 quarter milk samples revealed isolation of 11 types of bacterial species. E.coli was the predominant bacterium isolated from mastitic cases (30.4%) followed by S.aureus (28.07%), S.agalactiae (8.77%), S.epidermidis (8.47%), S.dysgalactiae (8.18%), S.uberis (7.89%), K.pneumoniae (3.21%), E.faecalis (2.04%), P.aeraginosa (2.04%), Serratia marcescens (0.58%) and Enterobacter aerogenes (0.29%). Among the clinically mastitic milk samples, the predominant bacterial isolate was E.coli (39.57%) followed by S.aureus (22.46%), S.uberis (9.09%), S.dysgalactiae (7.48%) and S.agalactiae (6.95%), but the predominant bacterial isolates recorded from subclinically mastitic milk samples was S.aureus (34.83%) followed by E.coli (19.35%), S.epidermidis (12.25%), S.agalactiae (10.96%), S.dysgalactiae (9.03%) and S.uberis (6.45%). Causative bacteria were isolated from mastitic quarter milk samples either singly as a sole agent of the disease with the percentage of 42.28% (44.36% and 40% from clinically and subclinically mastitic quarter milk samples, respectively) or mixed with other bacteria with the percentage of 57.72% (55.63% and 60% from clinically and subclinically mastitic milk samples, respectively). Serotyping of E.coli revealed 10 different serovars of E.coli according to somatic antigen namely 055 (29.8%), 0111 (14.42%), 0125 (9.61%), 0124 (8.65%), 044 (7.69%), 0119 (7.69%), 0128 (2.88%), 086 (2.88), 026 (1.92%) and 0114 (1.92%). In addition, 12.5% of the isolated E.coli strains could not be serologically identified by the available antisera. PCR technique was used as a rapid, sensitive and specific tool to detect the major pathogens causing mastitis (E.coli, S.aureus, S.agalactiae, S.dysgalaetiae and S.uberis). The chosen milk samples were tested first with one set of universal primers which were designed to detect these 5 pathogens in milk, then they were tested with one set of specific primers for detection of each of these pathogens or using multiplex PCR with the 5 species specific primers at the same annealing temperature. All these techniques had proven to be reliable since by comparing the results with in vitro culture technique revealed that PCR detected all the clinically and subclinically mastitic milk samples with positive bacteriological examination results, moreover it detected some of the milk samples from clinical and subclinical mastitis that yielded negative results by bacteriological examination (40% and 30%, respectively). In addition, it could detect these pathogens directly from milk. Results of antimicrobial sensitivity test revealed that the main bacterial pathogens isolated from clinical and subclinical mastitis cases were highly sensitive to gentamycin, chloramphenicol, nitrofurantoin, norfloxacin, neomycin sulphate and ciprofloxacin (94.79%, 86,45%, 86,45%, 86.45%, 82.29% and 79.16%, respectively). Sensitive to cefoperazone, cefotaxime, amikacine, erythromycin and amoxycillin/clavulanic acid (70.83%, 69.79%, 66.66%, 65.62% and 62.5%, respectively), but they were highly resistant to ampicillin and penicillin G (23.95% and 21.87%, respective