Sensitivity to Commonly Used Antibiotics of Staphylococcus aureus Strains Isolated from Mastitic Cows

Abstract

Twenty one clinically healthy cows were screened for subclinical mastitis. All the cows were in lactation and were maintained at the Sokoine University dairy units. Of 84 udder quarters examined, 37 (44.0 %) were positive for mastitis by the California mastitis test (CMT). Staphylococcus aureus was present in 18 quarters. Staphylococci were isolated and tested for sensitivity against antibiotics (cephalosporin, chloramphenicol, erythromycin, gentamicin, kanamycin, neomycin, penicillin, streptomycin, and tetracycline).Cephalosporin and gentamicin showed the largest zones of growth retardation, whereas penicillin, tetracycline and chloramphenicol showed the least retardation effect against S. aureus. Our findings emphasize the importance of carrying out in vitro sensitivity tests before instituting   antibiotic treatment.