Susceptibility test of the Mycobacterium avium complex to sixteen anti-infective agents

Abstract

To compare the in vitro activities of 13 anti-infective agents and 3 new quinolones (sitafloxacin, gatifloxacin and moxifloxacin) against Mycobacterium avium complex (MAC) isolates, and therefore to explore the possibility of using these quinolones to treat MAC diseases. The minimal inhibitory concentration (MIC) of the above 16 anti-infective agents, including sitafloxacin, gatifloxacin and moxifloxacin against MAC isolates was determined by using agar dilution methods, and then the MIC90s of the different anti-infective agents were compared. The MICs of M. avium isolates showed a wider range and was less sensitive to most of the anti-infective agents as compared with M. intracellulare isolates. The MIC90s of clarithromycin against M. avium and M. intracellulare isolates were 32 mg/L and 16 mg/L, respectively, which were the lowest among 4 macrolide compounds. The MIC90 of rifalazil were 0.5 mg/L and 0.25 mg/L, respectively, which were the lowest among 4 rifamycin compounds. The MIC90 of sitafloxacin against M. avium and M. intracellulare isolates were both 4 mg/L, which were the lowest among 5 quinolones. For gatifloxacin and moxifloxacin, the MIC90 against M. avium and M. intracellulare isolates were both 8 mg/L. Two clarithromycin-sensitive strains (MIC=0.5 mg/L) showed a similar MIC of the lower limit for other compounds. Three clarithromycin-insensitive strains (MIC=64 mg/L) showed a similar MIC of the upper limit for other compounds except quinolones. Rifalazil, sitafloxacin, gatifloxacin and moxifloxacin showed acceptable in vitro activities against MAC isolates.