Isoniazid resistance profile in rifampicin resistant Mycobacterium tuberculosis

In this cross-sectional study, from March 2021 to February 2022, a total 53 RIF resistant MTB isolates in sputum samples, detected by Xpert-MTB RIF assay were enrolled. All samples were tested for mutation in katG (codon 315) and inhA promoter (-5, -8, -15 and -16) genes for detection of INH resistance by Real-time PCR. Statistical analysis was done using SPSS (version-26). Out of 53 RIF resistant samples, the proportion of newly diagnosed and previously treated cases were nearly equal and most of the previously treated cases (92.9%) received treatment regularly. 15.1% RIF resistant MTB isolates were sensitive to INH and rest had concomitant resistance to INH. INH resistant cases were mostly previously treated (55.5%), whereas sensitive cases were mostly newly diagnosed (62.5%). katG was found to be the prominent mutation, with or without in combination with inhA mutation. A considerable number of RIF resistant isolates did not show concomitant resistance to INH. Most of the INH resistant isolates were associated with katG mutation. Evaluation of INH resistance before using high dose INH will help to avoid dose dependent toxicity and to determine an appropriate treatment regimen timely. Bangabandhu Sheikh Mujib Medical University Journal 2023;16(3): 160-166