In vitro antituberculosis activity of a new antibacterial substance ofloxacin (DL8280).

A new antituberculosis agent, ofloxacin (DL8280), inhibited the growth of Mycobacterium tuberculosis at concentrations of 0.63 to 1.25 micrograms/ml. There were no cross-resistance relationships between this agent and other antituberculosis agents. The agent delayed the growth rate of M. tuberculosis (strain H37Rv) at concentrations of 0.2 to 0.5 microgram/ml. It showed considerable bactericidal activity at concentrations a little higher than the growth-inhibitory concentration. The combined effect with other antituberculosis agents seemed to be additive. The pattern of resistance that developed with this agent was the obligatory two-step pattern, and there were 2 resistant phenotypes.