Outcomes of pulmonary MDR-TB: impacts of fluoroquinolone resistance and linezolid treatment

Objectives: Fluoroquinolones (FQs) are the most important second-line drugs for MDR-TB treatment. Therapeutic options for FQ-resistant (FQ-R) MDR/XDR-TB are very limited. The purpose of the present study was to determine treatment outcomes and risk factors associated with unfavourable outcomes of MDR/XDR-TB, focusing on the impacts of FQ-R status and linezolid treatment. Methods: This was a retrospective cohort study of 337 MDR-TB patients, including 144 (42.7%) FQ-R MDR/XDR-TB cases. Treatment outcomes were evaluated according to WHO 2013 recommendations. Results: Later-generation FQs such as levofloxacin or moxifloxacin were given to 331 (98.2%) patients. Overall, favourable outcomes were achieved in 272 (80.7%) patients. FQ-R second-line injectable drug-susceptible MDR [adjusted OR (aOR) 4.299, 95% CI 1.239-14.916, P = 0.015] and XDR status (aOR 6.294, 95% CI 1.204-32.909, P = 0.024) were independently associated with unfavourable outcomes. However, FQ-susceptible (FQ-S) secondl-ine injectable drug-resistant MDR status was not associated with unfavourable outcomes (aOR 1.814, 95% CI 0.314-10.485, P = 0.999). Favourable treatment outcomes were more frequent in FQ-R MDR/XDR-TB patients who received linezolid (82.8%) compared with those who did not receive linezolid (58.1%, P = 0.002). When FQ-R MDR/XDR-TB treatment without linezolid was used as a reference, the addition of linezolid was associated with favourable outcomes (aOR 4.081, 95% CI 1.237-13.460, P = 0.017), comparable to those for FQ-S MDR-TB (aOR 4.341, 95% CI 1.470-12.822, P = 0.005). Conclusions: Later-generation FQs could improve treatment outcomes of patients with MDR-TB. Linezolid should be considered for inclusion in FQ-R MDR/XDR-TB treatment regimens.