In vitro susceptibility of avian mycoplasmas to enrofloxacin, sarafloxacin, tylosin, and oxytetracycline

In vitro susceptibility of avian Mycoplasma gallisepricum (MG) and Myroplas ma synoviae (MS) to enrofloxacin, sarafloxacin, tylosin, and oxytetracyclin e was determined by a serial broth dilution method. The minimum inhibitory concentration (MIC) was recognized by a conversion of the pH indicator phen ol red in culture media to a yellow color. Each isolate or type strain of m ycoplasma was tested in two replicates. The MICs of tylosin, enrofloxacin, sarafloxacin, and oxytetracycline against five isolates and two reference s trains of MG (approximately 10(5) colony-forming units [CFU]/ml) were 0.05, 0.14, 0.37, and 1.30 mug/ml, respectively The MICs of the four antimicrobi al agents against six isolates and one reference strain of MS (approximate 10(5) CFU/ml) were 0.13, 1.82, 1.76, and 0.91 mug/ml, respectively There we re no differences (P > 0.05) between tylosin, enrofloxacin, and sarafloxaci n against MG, but these three antibiotics were different (p < 0.05) from ox ytetracycline. The MIC value of tylosin against: MS was different (P < 0.05 ) from those of sarafloxacin and enrofloxacin, but it was not different (P > 0.05) from that of oxytetracycline.