Antibiogram profile of Group B Streptococci isolated from bovine mastitis cases

Mastitis in bovines has become extremely complex and is one of the costliest disease in dairy industry. One important reason for treatment failure is assumed to indiscriminate use of antibacterial without testing in vitro sensitivity of causal organisms. This practice results in development of resistance to commonly used antimicrobials. To chalk out suitable antibiotic therapy, isolation and antibiotic sensitivity studies are always essential. Keeping these points in view the present study was undertaken to select a suitable antibiotic for treatment for Streptococcal mastitis. A total of 96 Streptococcal isolates were recovered from 261 milk samples collected from in and around Bangalore city, including fourteen milk samples from clinical mastitis cases which was confirmed by tuf gene based PCR. Out of 96 Streptococcal isolates, sixteen isolates including one reference strain were found to be S. agalactiae based on 16S rRNA and sip gene based PCR. The in vitro antibiogram study was conducted with fourteen antibiotics which were chosen according to their common use in research and veterinary practice. Investigation had shown that antibacterial susceptibility against S. agalactiae in following order, of sensitivity Ampicillin/ Sulbactum (94%), Chloramphenicol (81%), Gentamicin (69%), Ampicillin and Penicillin G (50%), Amoxycillin/Sulbactum and Streptomycin (37%), Piperacillin/Tazobactam (31%), Methicillin and Cefotaxime (25%), Enrofloxacin (19%), Ceftriaxone/Sulbactum and Ceftriaxone (12%) and Oxacillin (0%). Ampicillin/Sulbactum combination proved to be the drug of choice in this study.