1. Activities of ciprofloxacin and ofloxacin against rapidly growing mycobacteria with demonstration of acquired resistance following single-drug therapy.
- Author
-
Wallace RJ Jr, Bedsole G, Sumter G, Sanders CV, Steele LC, Brown BA, Smith J, and Graham DR
- Subjects
- Adult, Aged, Ciprofloxacin pharmacology, Drug Resistance, Microbial, Female, Humans, Male, Microbial Sensitivity Tests, Middle Aged, Mutation, Mycobacterium genetics, Mycobacterium Infections microbiology, Ofloxacin pharmacology, Skin Diseases, Infectious microbiology, Ciprofloxacin therapeutic use, Mycobacterium drug effects, Mycobacterium Infections drug therapy, Ofloxacin therapeutic use, Skin Diseases, Infectious drug therapy
- Abstract
The susceptibility to ciprofloxacin of 548 clinical isolates of rapidly growing mycobacteria belonging to eight subgroups or species was determined. The 170 isolates of Mycobacterium fortuitum biovar.fortuitum were most susceptible; the MIC for 90% of the organisms was 0.125 micrograms/ml. The other biovariants of M. fortuitum, M. smegmatis, and the M. chelonae-like organisms were less susceptible; the modal MIC was 0.5 micrograms/ml, and the MIC for 90% of organisms was 1.0 micrograms/ml. The two subspecies of M. chelonae were generally resistant, with only 8% of 206 isolates falling in the moderately susceptible category (MIC, 2 micrograms/ml) and only 2% falling in the susceptible category (MIC, less than or equal to 1 micrograms/ml). MICs of ofloxacin averaged 1 to 2 dilutions higher than those of ciprofloxacin for all subgroups tested. Three patients with M. fortuitum cutaneous disease relapsed after an initial response to therapy with ciprofloxacin, and their isolate was shown to have acquired drug resistance. Mutational frequencies for M. fortuitum with ciprofloxacin were relatively high (10(-5) to 10(-7), and MICs for single-step mutants were similar to those for the clinically resistant strains. Thus, despite the excellent activity of ciprofloxacin against rapidly growing mycobacterial groups other than M. chelonae, single-drug therapy should be used with caution because of the risk of development of mutational resistance.
- Published
- 1990
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