Characterization of linezolid-resistance-associated mutations in Mycobacterium tuberculosis through WGS.

Abstract

OBJECTIVES\nLinezolid is becoming an important antibiotic for treating MDR/XDR TB, but the mutations conferring resistance to linezolid remain inadequately characterized. Herein, we investigated the linezolid-resistance-associated mutations on a whole-genome scale through parallel selections of resistant isolates in vitro.\n\n\nMETHODS\nTen parallel Mycobacterium tuberculosis H37Rv cultures were subjected to spontaneous mutant selection on 7H11 agar plates containing 2.5\u2009mg/L linezolid. The linezolid resistance of resulting colonies was confirmed by growth on a second linezolid plate. WGS was then performed to identify mutations associated with linezolid resistance.\n\n\nRESULTS\nOf 181 colonies appearing on the initial linezolid plates, 154 were confirmed to be linezolid resistant. WGS showed that 88.3% (136/154) of these isolates had a T460C mutation in rplC, resulting in a C154R substitution. The other 18 isolates harboured a single mutation in the rrl gene, with G2814T and G2270T mutations accounting for 7.8% (12/154) and 3.9% (6/154), respectively.\n\n\nCONCLUSIONS\nNo mutations in novel genes were associated with linezolid resistance in a whole-genome investigation of 154 linezolid-resistant isolates selected in vitro. These results emphasize that rrl and rplC genes should be the major targets for molecular detection of linezolid resistance.