In vitro antimycobacterial activity of a new quinolone, levofloxacin (DR-3355).

OBJECTIVE: To examine in vitro antimycobacterial activity of levofloxacin.
DESIGN: Minimum inhibitary concentrations (MICs) of levofloxacin for various mycobacterial species were determined by the agar dilution method using 7H11 medium and compared with those of ofloxacin. Antimicrobial activity of levofloxacin against Mycobacterium tuberculosis and M. intracellulare phagocytosed in murine peritoneal macrophages was measured in terms of reducing cell-associated bacterial colony forming units (CFUs).
RESULTS: MICs of levofloxacin against M. tuberculosis, M. kansasii, M. marinum, M. scrofulaceum, M. avium, M. intracellulare, M. fortuitum, and M. chelonae were 2 to 4 times lower than those of ofloxacin. Levofloxacin exhibited higher efficacy in reducing bacterial CFUs in macrophages than ofloxacin.
CONCLUSION: Levofloxacin possessed more potent in vitro antimycobacterial activities as compared to that of ofloxacin.