Rapid, inexpensive MIC determination of Mycobacterium tuberculosis isolates by using microplate nitrate reductase assay.

A rapid colorimetric, microplate-based nitrate reductase assay (NRA) method for antibiotic susceptibility profile of clinical isolates of Mycobacterium tuberculosis was compared with Alamar Blue assay (ABA). The results obtained by both the methods were also compared with conventional agar proportion method. The overall agreement between the results obtained by NRA and ABA was 99% and 98%, respectively, when compared with agar proportion method. Reproducible results for all the isolates were obtained within 8 days by NRA as well as ABA. The specificity of NRA method for M. tuberculosis makes it more suitable method for MIC determination.