Prevalence of Bedaquiline Resistance among Drug Resistant - Tuberculosis Cases at a Tertiary Healthcare Setting in Metropolitan City of Maharashtra, India.

BACKGROUND: Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains the leading cause of death from a single infectious agent worldwide. Drug-resistant TB (DR-TB) poses a major challenge. Bedaquiline (BDQ) is central to multidrug resistant tuberculosis/extensively drug-resistant TB (MDR/XDR-TB) treatment, yet emerging resistance prompted this study to assess its prevalence.

METHODS: This prospective observational study was conducted in the TB culture and drug susceptibility testing (DST) laboratory of a tertiary care hospital over 9 months. Sputum samples from presumptive DR-TB cases were included, whereas extrapulmonary and nontuberculous mycobacteria samples were excluded from the study.

RESULTS: A total of 1190 samples were subjected to the first-line probe assay (LPA) for drug resistance detection in MTB. MDR-TB was most common, followed by mono-isoniazid and monorifampicin resistance. Of 512 DR-TB samples tested by second-line probe assay (SL-LPA), 25 yielded invalid results. Fluoroquinolone (FQ) resistance was highest (47.7%), whereas second-line injectable drug (SLID) resistance was rare (1.4%); combined FQ + SLID resistance occurred in 10.7% samples, whereas 35.4% samples were sensitive. Among 380 isolates subjected to liquid culture DST, resistance was detected to moxifloxacin (7.4%), linezolid (2.1%), and BDQ (0.78%).

CONCLUSION: BDQ resistance is low but emerging; routine DST, rational drug use, and robust surveillance are vital to preserve BDQ efficacy and ensure effective DR-TB management.