Evaluation of the Performance of Nitrate Reductase Assay for Rapid Drug-Susceptibility Testing of Mycobacterium Tuberculosis in South Gujarat Region

The objective of the study was to evaluate the performance of nitrate reductase assay (NRA) as a rapid, reliable and inexpensive method for drug-susceptibility testing (DST) of Mycobacterium tuberculosis against first line antitubercular drugs, such as isoniazid (INH), rifampicin (RIF), ethambutol (EMB), streptomycin (STR). In total, 230 isolates were subjected to test by proportion method (PM) and NRA. By comparing the results of NRA with those of the gold standard PM, Sensitivity values for isoniazid, rifampicin, ethambutol and streptomycin were 98.7 %, 100 %, 98.3 % and 97.3 %, respectively and specicity values were 100 %, 100 %, 100 % and 96.7 %, respectively. The median time of obtaining results was shorter using NRA (10 days) compared to PM (28 days). An excellent agreement was observed between the two phenotypic tests was 98.8 %. The results demonstrated that NRA is suitable for the early determination of INH and RIF resistance and has the potential to be a useful tool for rapid drug-sensitivity test of M. tuberculosis in low resource settings.