Sensitivity of certain porcine and bovine mycoplasmas to antimicrobial agents in a liquid medium test compared to a disc assay.

The sensitivity of some porcine and bovine mycoplasmas to potent antimicrobial agents was examined. Minimal inhibitory concentration (MIC) values were estimated for M. hyosynoviae, M. hyopneumoniae, M. dispar and M. bovis against enrofloxacin, lincomycin, tetracycline, tiamulin and tylosin, in a liquid medium test and in a disc assay. All 6 examined strains of each species and the respective type strains were significantly inhibited. The greatest sensitivity was noted for tiamulin against strains of M. hyosynoviae with a final MIC50 broth value of 0.025 micrograms ml-1 and disc value of 0.03 microgram per disc. Enrofloxacin was found very potent against M. hyopneumoniae with a final MIC50 of 0.025 microgram ml-1 and 0.1 microgram per disc, and for M. dispar with 0.05 microgram ml-1 and 0.03 microgram per disc. Most disc assay estimates in micrograms per disc were similar to or moderately greater than corresponding final broth figures in microgram ml-1. It may be possible to convert observed disc assay values into representative final broth MIC values for use in the clinic.