Comparison of in vitro activities of gatifloxacin and ciprofloxacin against four taxa of rapidly growing mycobacteria.

By using current NCCLS broth microdilution methods, we found that gatifloxacin inhibited 90% of the isolates of the Mycobacterium fortuitum group at < or =0.12 micro g/ml and 90% of the Mycobacterium chelonae isolates at < or =4 micro g/ml. Gatifloxacin was generally fourfold more active than ciprofloxacin. We recommend that both gatifloxacin and ciprofloxacin be tested routinely against rapidly growing mycobacteria.