In-vitro susceptibility of mycobacteria to ciprofloxacin

Two hundred and seventy-six strains of mycobacteria were tested for susceptibility to ciprofloxacin (Bay 0 9867), a 4-quinolone antimicrobial agent. Most strains of Mycobacterium tuberculosis, Myco. fortuitum, Myco. kansasii, Myco. marinum and Myco. xenopi were sensitive to minimum inhibitory concentrations (MICs) of 0.78-1.56 mg/l, equivalent to resistance ratios of 1 or 2. Most strains of Myco. avium-intracellulare and Myco. chelonei required MICs of 12.5 mg/l or more, giving resistance ratios of 8.