Comparison between the minimal inhibitory concentration of tilmicosin and oxytetracycline for bovine pneumonic Pasteurella haemolytica isolates.

The minimal inhibitory concentration (MIC) of tilmicosin and oxytetracycline was determined for Pasteurella haemolytica isolated from Dutch cattle in 1991. The agar dilution method was used. Of the Pasteurella haemolytica strains examined, 96% (24) had a MIC for tilmicosin of 2 micrograms/ml or lower; in one strain the MIC was 8 micrograms/ml. The MIC for oxytetracycline was equal to or higher than 64 micrograms/ml in 19 strains (76%), whereas for 5 strains the MIC was 1 microgram/ml and for 1 strain 2 micrograms/ml.