IN-VITRO SUSCEPTIBILITIES OF RAPIDLY GROWING MYCOBACTERIA TO NEWER ANTIMICROBIAL AGENTS

The in vitro antimicrobial susceptibilities of 42 isolates of rapidly growing mycobacteria (Mycobacterium fortuitum, M. chelonae, and Mycoba cterium species [other than M. fortuitum and M. chelonae]) to nine qui nolones, including newer agents, two new aminoglycosides, and an amino cyclitol (trospectomycin) were determined by a broth microdilution met hod. The new quinolones, PD 117596, PD 127391, and PD 117558, showed e xcellent in vitro activities against M. fortuitum (MICs for 90% of iso lates [MIC90s], 0.06, 0.06, and 0.12 mug/ml, respectively). The MIC90 of ciprofloxacin for M. fortuitum was 0.5 mug/ml. Only 14 to 28% of is olates of M. chelonae were susceptible to various quinolones. Most iso lates of all three species were susceptible to the new aminoglycosides SCH 21420 and SCH 22591. The MIC90s of trospectomycin were 8 mug/ml f or M. chelonae, 32 mug/ml for Mycobacterium species, and >64 mug/ml fo r M. fortuitum.