In vitro activity of linezolid against multidrug-resistant Mycobacterium tuberculosis isolates.

Information in the literature regarding the activity of linezolid against multidrug-resistant (MDR) Mycobacterium tuberculosis strains is scarce. We therefore tested the in vitro activity of this drug against 39 MDR M. tuberculosis strains isolated from clinical specimens using the Bactec 460 TB system. All strains were inhibited by < or = 8 mg/L (minimum inhibitory concentration (MIC); MIC50 = 4 mg/L, MIC90 = 8 mg/L). Although the MIC values are higher than in other studies, based on proposed breakpoints all strains were found to be susceptible to linezolid. Further investigations to prove its usefulness in the treatment of MDR tuberculosis should be carried out.