Isoniazid resistance pattern among pulmonary tuberculosis patients in Bangladesh: an exploratory study.

Objectives: In high TB burden countries like Bangladesh, research and policies tend to focus on rifampicin (RIF)-resistant TB patients, leaving RIF sensitive but isoniazid (INH) resistant (Hr-TB) patients undiagnosed. Our study aims to determine the prevalence of INH resistance among pulmonary TB (PTB) patients in selected healthcare facilities in Bangladesh.
Methods: This study was conducted across nine TB Screening and Treatment Centers situated in Bangladesh. Sputum samples from 1084 Xpert-positive PTB patients were collected between April 2021 and December 2022, and cultured for drug susceptibility testing (DST). Demographic and clinical characteristics of Hr-TB and drug-susceptible TB patients were compared.
Results: Among available DST results of 998 culture positive isolates, resistance rate of any INH regardless of RIF susceptibility was 6.4% (64/998, 95% CI, 4.9-8.2). The rate was significantly higher in previously treated (21.1%, 16/76, 95% CI, 12.0-34.2) compared to newly diagnosed TB patients (5.2%, 48/922, 95% CI, 3.8-6.9) (p <0.001). The rate of Hr-TB was 4.5% (45/998, 95% CI, 3.3-6.0), which was also higher among previously treated (6.6%, 5/76, 95% CI, 1.4-13.5) compared to newly diagnosed TB patients (4.3%; 40/922, 95% CI, 3.1-5.9) (p=0.350). Most importantly, the rate of Hr-TB was more than double compared to MDR-TB (4.5%, 45/998, vs 1.9%, 19/998) found in the current study.
Conclusions: This study reveals a high prevalence of Hr-TB, surpassing even that of the MDR-TB in Bangladesh. This emphasizes the urgent need to adopt WHO-recommended molecular tools at the national level for rapid detection of INH resistance so that patients receive timely and appropriate treatment.
(Copyright © 2024. Published by Elsevier Ltd.)