Comparative evaluation of drug susceptibility testing of Mycobacterium tuberculosis by Nitrate reductase assay on direct sputum samples and Conventional proportion method
Abstract
Background and Objectives: The routinely used methods for anti-tubercular drug susceptibility testing are either costly or slow. As the prevalence of multidrug-resistant strains is increasing, the need for fast, reliable, and inexpensive methods that can be applied in settings with limited resources is essential.
Methods: It was a study of 100 sputum samples from smear positive patients at RNTCP centre. The samples were subjected to anti-tubercular drug susceptibility by Nitrate reductase assay on direct sputum samples and the routine indirect Conventional proportion method for two primary anti-tubercular drugs, i.e., Isoniazid, and Rifampicin.
Results: Out of 100 samples, 94 were sensitive to Isoniazid and Rifampicin by both Conventional Proportion Method, and Nitrate Reductase Assay. Four isolates were detected as MDR-TB strains (resistant to both Isoniazid and Rifampicin) and two were resistant only to Isoniazid by both the methods.
Conclusion: Drug susceptibility detected by Nitrate Reductase Assay has excellent agreement with the gold standard Conventional proportion method for Mycobacterium tuberculosis in our study. Hence in countries like India, where there is burden of tuberculosis cases and especially of drug resistant cases, NRA is a very valuable tool in the detection, treatment and follow up of tuberculosis cases for drug resistance.
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References
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