Antimicrobial susceptibility of Mycoplasma hyorhinis

A broth microdilution technique was used to determine the antimicrobial sus ceptibility of 15 field isolates of Mycoplasma hyorhinis to 10 antimicrobia l agents, representative of different classes, and contrasting newer agents to existing ones. For the macrolides, the MIC90 for tylosin and tilmicosin was 1 and 4 mu g/ml. respectively, but was greater than or equal to 16 mu g/ml for erythromycin. Tetracycline, lincomycin and enrofloxacin each had a n MIC90 of 2 mu g/ml. The mycoplasma had similar levels of susceptibility t o the aminoglycoside and aminocyclictol classes exhibiting an MIC90 of 4 mu g/ml for gentamicin and 2 mu g/ml for spectinomycin. The isolates exhibite d high MICs to trimethoprim/sulfamethoxazole with an MIC(90)greater than or equal to 16/304 mu g/ml. In summary, M. hyorhinis isolates from the US had low MICs against a variety of antimicrobials tested, with the exception of erythromycin and trimethoprim/ sulfamethoxazole. (C) 2000 Elsevier Science B.V. All rights reserved.