In vitro activity of linezolid against clinical isolates of Mycobacterium tuberculosis, including multidrug-resistant and extensively drug-resistant strains from Beijing, China.

The in vitro activity of linezolid was evaluated against 84 clinical isolates of Mycobacterium tuberculosis, including multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains, isolated from the center for tuberculosis research and treatment of the Chinese army. Linezolid showed excellent activity, with minimum inhibitory concentrations (MICs) of 0.125-0.5 μg/mL against all tested isolates. There were no differences in the MIC(50) and MIC(90) of linezolid between susceptible, isoniazid-resistant, MDR, and XDR. Indeed, all of the groups displayed identical MIC(90) values of 0.25 μg/mL, which is lower than previously reported in similar studies. We conclude that linezolid may be a more effective drug against M. tuberculosis and may play an important role in treating drug-resistant tuberculosis in China.