Drug susceptibility test of Mycobacterium tuberculosis by nitrate reductase assay

Drug susceptibility testing for Mycobacterium tuberculosis (M. tuberculosis) is especially required in difficult cases of tuberculosis (TB) chemotherapy and in cases of multidrug resistance (MDR-TB; combined resistance to isonizid and rifampicin with or without resistance to any other drug). The methods for in vitro cultivation and drug susceptibility testing (DST) of M. tuberculosis are cumbersome and not readily adaptable in most routine laboratories, particularly those in the developing world due to limited resources and lack of political will in those countries. A simple and cost effective method, the nitrate reductase assay (NRA), was compared with the gold standard proportion (egg bases Lowenstein Jensen's [LJ]) method for DST of M. tuberculosis in order to substantiate its suitability for routine use in Nigeria and in other countries of the developing world with high TB endemicity.