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

In high tuberculosis (TB) burden countries such as Bangladesh, research and policy 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 patients in selected health care facilities in Bangladesh.

This study was conducted across nine TB Screening and Treatment Centres situated in Bangladesh. Sputum samples from 1084 Xpert-positive pulmonary TB patients were collected between April 2021 and December 2022 and cultured for drug susceptibility testing. Demographic and clinical characteristics of Hr-TB and drug-susceptible TB patients were compared.

Among available drug susceptibility testing results of 998 culture-positive isolates, the 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 with 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 patients (6.6%, 5/76, 95% CI: 1.4-13.5) compared with 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 with MDR-TB (4.5%, 45/998, vs. 1.9%, 19/998) found in the current study.

This study reveals a high prevalence of Hr-TB, surpassing even that of the multi-drug-resistant 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.