In vitro activity of the new difluorinated quinolone sparfloxacin (AT-4140) against Mycobacterium tuberculosis compared with activities of ofloxacin and ciprofloxacin

MICs of the new fluoroquinolone drugs ofloxacin, ciprofloxacin, and sparfloxacin (AT-4140) for 10 strains of Mycobacterium tuberculosis were determined by using both a BACTEC radiometric method and testing on solid 7H11 agar medium. Radiometric MICs by 7H12 broth testing ranged from 0.5 to 1.0, 0.25 to 0.5, and 0.1 to 0.2 microgram/ml for ofloxacin, ciprofloxacin, and sparfloxacin respectively, whereas MICs in solid medium ranged from 0.5 to 1.0, 0.5 to 1.0, and 0.2 to 0.5 microgram/ml, respectively. The bactericidal action of the quinolones compared with their reported peak concentrations in human serum showed that sparfloxacin is the most bactericidal, followed by ciprofloxacin and ofloxacin. Our results suggest the potential of the new difluorinated quinolone sparfloxacin for use against the tubercle bacillus and indicate that further determination of its antimycobacterial spectrum and intracellular efficacy may be fruitful.