The Thai Journal of Veterinary Medicine


Bovine mastitis has had a great impact on the economic losses of the dairy industry. Nowadays, environmental pathogens cause the main types of bovine mastitis, especially the streptococci. The aim of the study was to identify the major Streptococcus species causing bovine mastitis in Taiwan as well as to reveal their antimicrobial susceptibility profiles. By colony morphology identifying, Gram staining, and subculturing on Edwards agar, the preliminary identified streptococci were subjected to biochemical identification, latex agglutination tests and dick diffusion tests for susceptibility tests of 16 antimicrobial agents. Among a total of 157 strains, Streptococcus uberis was the most dominant species found, followed by S. bovis, S. dysgalactiae, S. agalactiae, S. equinus and S. mitis. Most of them were sensitive to all the β-lactams we selected in the study, including amoxicillin, cefuroxime, cefazolin, bacitracin, ceftiofur, cloxacillin, penicillin and ampicicllin. However, high resistant rates were observed to aminoglycosides, tetracyclines and lincomycin. S. uberis was the main environmental mastitis causative pathogens in the present study. Beta-lactams were the effective antimicrobials agents against them.

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