MINIMUM INHIBITORY CONCENTRATION BREAKPOINTS AND DISK DIFFUSION INHIBITORY ZONE INTERPRETIVE CRITERIA FOR TILMICOSIN SUSCEPTIBILITY TESTINGAGAINST PASTEURELLA SPP ASSOCIATED WITH BOVINE RESPIRATORY-DISEASE

Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. The first tilmicosin-containing product was a pproved to treat bovine respiratory disease associated with pasteurell ae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficac y studies that demonstrated a favorable therapeutic outcome, on pharma cokinetic data, and on in vitro test data, as recommended by the Natio nal Committee for Clinical Laboratory Standards (NCCLS). The NCCLS-app roved breakpoints for the MIC dilution testing are resistant greater t han or equal to 32 mu g/ml, intermediate 16 mu g/ml, and susceptible l ess than or equal to 8 mu g/ml. The zone of inhibition interpretive cr iteria for disk diffusion testing with a 15-mu g disk are resistant le ss than or equal to 10 mm, intermediate 11-13 mm, and susceptible grea ter than or equal to 14 mm.