In vitro bactericidal assay of linezolid on multidrug-resistant tuberculosis and nontuberculous mycobacteria / 中华检验医学杂志

ABSTRACT

Objective To investigate the mycobactericidal efficacy of linezolid on multidrugresistant tuberculosis (MDR-TB) and nontuberculous mycobacteria (NTM) in vitro.Methods Seven hundred and sixty-two Mycobacterium tuberculosis and 20 NTM isolates from Hangzhou were identified by using hsp65 gene sequencing from March to June,2013.Seventy MDR-TB isolates,which were screened by using proportion method,and twenty NTM isolates were tested the MIC to linezolid,and the differences of MICs to linezolid between MDR-TB and NTM werw analyzed in vitro.Results All 70 MDR-TB isolates were inhibited at concentrations of ≤ 1 mg/L by linezolid,MIC50 was 0.5 mg/L and MIC90 1 mg/L.Of all 8 isolates inhibited at concentration of 1 mg/L,there were 6 isolates resistant to isoniazid,rifampin,streptomycin and ethambutol,suggesting this resistance pattern may reduce sensitivity to linezolid.Among the NTM isolates,18 Mycobacterium intracellulare isolates,whose MICs to linezolid at 8-16 mg/L,were non-resistant isolates,while 2 Mycobacterium abscessus isolates displaying MICs ＞ 32 mg/L,were resistant to linezolid.Conclusions Linezolid showed great activity to MDR-TB and there were no linezolid-resistant MDR-TB isolates identified in this study.However,MICs of MDR-TB against linezolid increased with their resistant numbers to first-line agents.This study also showed that different NTM species have varied sensitivity to linezolid.