IN VITRO ANTIMYCOBACTERIAL ACTIVITY OF A NEW QUINOLONE, T-3761

Abstract

We evaluated the in vitro antimicrobial activity of T-3761 and ofloxacin againstrepresentative pathogenic mycobacteria by the agar dilution method, using 7H11 agarmedium. T-3761 showed appreciable antimicrobial activity against Mycobacteriumtuberculosis (MIC₉₀: 3.13μg/ml), M. kansasii (MIC₉₀: 6.25μg/m/) and M. fortuitum (MIC₉₀: 3.13μg/ml), whereas the agent was not active against M. marinum (MIC₉₀: 25μ g/ml), M. scrofulaceum (MIC₉₀: 50μg/ml), M. avium (MIC₉₀: >100μg/ml), M. intracellulare (MIC₉₀: >100μg/m/), M. chelonae subsp. abscessus (MIC₉₀: >100 μg/ml) andM. chelonae subsp. chelonae (MIC₉₀: 50μg/ml). The in vitro antimicrobial activity of T3761 against M. fortuitum was a little more potent than that of ofloxacin, whereas theactivity of T-3761 against the other mycobacteria was slightly inferior to that ofofloxacin. The antimycobacterial activity of T-3761 against M. tuberculosis H37Rv (MICin vitro: T-3761=3.13μg/ml, OFLX=0.78μg/ml) phagocytosed in murine peritonealmacrophages was less active than that of ofloxacin, when the macrophages were cultured inRPMI-1640 medium containing 1μg/ml or 10μg/m/ of these agents for up to 5 days. Theactivity of 10μg/ml of T-3761 was equivalent to that of 1μg/ml of ofloxacin.