Fluroquinolone drug resistance among MDR-TB patients increases the risk of unfavourable interim microbiological treatment outcome: An observational study

Abstract

Objectives: Sputum culture conversion at the end of the intensive phase of multidrug-resistant tuberculosis (MDR-TB) treatment is a key predictor for successful treatment outcome. This observational study was undertaken to assess the interim microbiological outcome of a cohort of rifampicin-resistant (RR)-TB patients with variable resistance to second-line drugs.

Methods: During Jan-Apr 2018, we consecutively enrolled 100 RR-TB patients, who underwent phenotypic drug susceptibility testing (DST) to assess baseline resistance to second-line drugs. Following RR-TB diagnosis, these patients were started on MDR-TB treatment. After 6 months of treatment, sputum culture conversion status was determined. Data were analysed to assess the impact of resistance to second-line drugs on culture conversion.

Results: DST of 100 RR-TB patients showed a high resistance to fluoroquinolones (FQs; levofloxacin 56%; moxifloxacin 44%) followed by kanamycin (8%) and capreomycin (6%). None of the patients were resistant to the other drugs tested (amikacin, clofazimine and linezolid). At 6-month treatment follow-up, 28 patients had been lost to follow-up and eight had died. Microbiological outcome was obtained from the remaining 64 patients, but successful culture conversion was achieved in only 62.5% of the patients. FQ resistance was found to be a strong predictor (P<0.001) for unfavourable microbiological outcome.

Conclusion: The rate of FQ resistance in RR/MDR-TB is high and has strong association with unsuccessful interim microbiological outcome of conventional MDR-TB treatment.

Keywords: Culture conversion; Fluoroquinolone resistance; Multidrug resistant tuberculosis; Rifampicin resistant tuberculosis; Treatment outcome.