IN-VITRO EVALUATION OF VARIOUS ANTIMICROBIALS AGAINST MYCOPLASMA-GALLISEPTICUM AND MYCOPLASMA-SYNOVIAE BY THE MICRO-BROTH METHOD, AND COMPARISON WITH A COMMERCIALLY-PREPARED TEST SYSTEM

The efficacy of danofloxacin, a new quinolone antimicrobial agent, was tested in vitro by the micro-broth method with nine field strains of Mycoplasma gallisepticum (Mg and eight of M. synoviae (Ms) and compari son was made with oxytetracycline and tylosin tartrate. The virulent S 6 strain of Mg was also included for reference. All Mycoplasma strains , including a strain of Mg that was resistant to tylosin tartrate, wer e susceptible to danofloxacin with minimal inhibitory concentrations r anging from less-than-or-equal-to 0.008 to 0.5 mug/ml. A commercially produced test system (Sensititre(R)), using micro-plates whose wells w ere predosed with antimicrobial agents and then dried, was also invest igated. Results with the same three antimicrobials were in agreement w ith those obtained by the micro-broth method. With the exception of th e tylosin resistant strain, the Mg strains were more susceptible to er ythromycin than the Ms strains. Conversely, Ms strains were susceptibl e to apramycin, while the Mg strains appeared to be resistant.