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Objective: To examine the prevalence of clinical and
subclinical bovine mastitis and determination of minimum
inhibitory cocentration (MIC) in the original bacteria
(such as staphylococus aureus(S.aureus) and Escherichia
coli(E coli) responsible for this disease. Animals: Three hundred thirty eight cows from 8 herds. Design: Cross sectional study
Statistic analysis: Descriptive study.
Procedure: Milk samples were collected from 1352
quarters of 338 cows in eight farms at the morning milking.
California mastitis test (CMT) was carried out on each
sample. Isolation, identification of bacteria and
determination of minimum inhibitory concentration (MIC)
were carried out in the laboratory. Results: The MIC and MBC of antibiotics
(Chloramphenicol, Cephalexin, Amoxicillin, Ampicillin,
Tetracycline, Streptomycin, Enrofloxacin, Gentamicin)
were carried out against 200 bacterial isolates including 118
E. coli and 82 S. aureus isolated from bovine mastitis.
Antimicrobial susceptibility testing showed that all the
isolates were sensitive to Gentarnicin and Enrofloxacin and
resistant to Penicillin. The occurrence of clinical and subclinical mastitis were 6.80 arid 67.45 percent in herds,
respectively.While the MIC values higher than 100 jig/ml
for 9 antibiotics (Chlorarnphenicol, Cephalexin,
Amoxicillin, Ampicillin, Penecillin, Tetracycline, Streptomycin, Enrofloxacin, Gentamicin) against E.coli
were 11.0, 0, 12.2, 20.7, 100, 22, 15.9, 0 and 0 %, these
values against S.aureus werel5.3, 0, 30.3, 0, 100,38.1,48.3, 0 and 0 %, respectively. On the other hand, while, the MBC
levels for these antibiotics against E.coli were 40.2, 19.5,
96.3,48.7, 100,74.4, 29.3, 0 and 0% these values against S.
aureus were 46.6, 13.5, 84.7, 100, 100, 100, 89, 0%,
respectively. J.Fac. Vet.Med. Univ. Tehran. 60,3:247- 252,2005.