Antibiotic susceptibility of staphylococci isolated from bovine subclinical mastitis

A total of 365 isolates of staphylococci including 209 S. aureus and 156 coagulase negative staphylococci (CNS) isolated from subclinical cases of bovine mastitis in Ahvaz (Iran) were analyzed for their susceptibility to several antimicrobial agents by agar disk diffusion method. Out of 209 isolates of S. aureus resistance was detected in 120 (57.42%), 64 (30.62%), 29 (13.88%), 29 (13.88%) and 10 (4.78%) isolates for penicillin, streptomycin, erythromycin, tetracycline and trimethoprim-sulfamethoxazol, respectively. No resistance was detected for gentamicin. Out of 156 CNS isolates resistance was detected in 48 (30.19%), 24 (15.09%), 20 (12.58%), 24 (15.09%) and 9 (5.66%) isolates for penicillin, streptomycin, erythromycin, tetracycline and trimethoprim-sufamethoxazol, respectively, whereas no resistance was detected for gentamicin. Results indicated that these isolates exhibited the highest degree of resistance to penicillin of all antimicrobial agents tested.