Correlation of mutations with the minimum inhibitory concentrations of isoniazid drug among isoniazid-resistant Mycobacterium tuberculosis isolates in Bangladesh

Abstract

Tuberculosis is still one of the major causes of mortality in the globe. Isoniazid (INH), a first-line medication used to treat tuberculosis is becoming increasingly resistant. With the rise of INH resistance we need more data on the genes responsible for the mutations and their correlated MIC values. In our study, we tested the MIC (Minimal inhibitory concentration) of 47 INH resistant Mycobacterium tuberculosis isolates that were obtained from Xpert MTB/RIF positive pulmonary tuberculosis patients diagnosed from TB Screening and Treatment Centers located at Dhaka, Sylhet and Chittagong divisions. Xpert XDR assay has been used in this study, which is a nested real time PCR application that can detect Mycobacterium tuberculosis as well as resistance to six leading antibiotics for TB treatment - INH (isoniazid), AMK (amikacin), KAN (Kanamycin), CAP (Capreomicin), FLQ (Fluroquinolone), and ETH (Ethionamide). The four most prevalent mutations that are responsible for INH resistance- KatG, inhA, fabG147 and ahpC can also be detected with the Xpert/XDR assay. About 485 of the isolates were tested by the Xpert/XDR assay. Isoniazid (INH) resistant samples were identified and were further tested for MIC (Minimal inhibitory concentration) on a 96-well plate ranging from 0.0156 ug/ml to 8 ug/ml. Among 485 isolates tested for Xpert/XDR assay, 47 were found to be INH resistant. The Xpert XDR assay results INH of mutation regions were then compared with the MIC value of the respective isolate. It was found that among the 47 INH Resistant samples examined for MIC, those with the KatG mutation had the highest MIC value - 8 ug/ml - and also the highest frequency among the isolates, accounting for about 61.7% (29 isolates). The mutation in the inhA promoter region was found in around 25.53% (12 isolates) of the isolates, having MIC values ranging from 0.03125 ug/ml to 2 ug/ml. The ahpC and FabG1 genes had the fewest cases, each accounting for one case with a modest MIC value of 1 ug/ml. In a few cases, double mutations have been identified, which are thought to lead to a higher MIC value. This study provides some insight into the frequency of INH resistance patterns in this country, as well as the related MIC values with the most prevalent mutations. More research and data are required in order to clearly anticipate the INH drug resistance mutation pattern and the drug concentration associated with the mutations in order to battle MDR-TB/XDR-TB and resist AMR (Antimicrobial resistance) in the field of tuberculosis.