Prevalence and Antibiotic Susceptibility of Streptococcus spp. in Cows with Mastitis in Germi, Iran

Streptococci are frequently isolated from bovine mastitis in dairy cows with only limited information about the antimicrobial susceptibility of these organisms. The aim of this study was to investigate the prevalence of Streptococcus agalactiae isolated from clinical cases of bovine mastitis in Germi, Iran; and determine their susceptibility to some antibiotics. 700 milk samples collected from traditional and industrial dairy cattle husbandry suspected of having mastitic udders were submitted to laboratory for bacteriologic identification by biochemical and serological methods. The susceptibility patterns were studied by agar disk diffusion methods (ADDM). A total of 525 (75%) of the milk samples streptococci isolate belonging to 3 species namely S. agalactiae (52.95%), S. dysgalactiae (25.57%) and S. uberis (18.48%). All of isolates were resistant to streptomycin. Sensitivity to other antibiotics tested was varied. In comparison with other antibiotics amoxicillin and cephalexin were the most effective, in vitro. These species of streptococcus are of great public importance and the antibiotic susceptibility tests should be performed together with the identification of the bacterial agents in order to achieve effective treatment.