Direct Nitrate Reductase Assay for detection of drug resistance in Mycobacterium tuberculosis: rapid, simple and inexpensive method for low resource laboratories

Abstract

INTRODUCTION: The most common method for detection of drug-resistant-Tuberculosis (DR-TB) in resource-limited settings (RLSs) is indirect susceptibility testing on Lowenstein-Jensen (LJ) medium with results available only after 2-3 months. Rapid detection of drug resistance by direct Nitatre Reductase Assay (NRA) expedites Tuberculosis patient management. The objective of the study is to access the feasibility and performance of Direct NRA for detection of DR-TB in National Tuberculosis Center under the National Tuberculosis Control Programme (NTP).MATERIALS AND METHODS: Out of 416 previously treated and new pulmonary TB suspect cases; a total of 117 (28.1%) smear-positive sputa with a positivity score of 1+ or more were used in the study. The NRA results were compared with the gold standard LJ proportion method for 110 (94%) specimens while 7 were either contaminated or culture negative.RESULTS: In comparison with LJ proportion method, the respective sensitivities, specificities, NPV, PPV and kappa agreement were 97.2% (95% CI, 86-100), 95.9%(95% CI, 89-99), 92.1% (95% CI, 78-99) 98.6% (95% CI, 92-100), and 0.92 for INH, 100% (95%CI, 90-100), 98.7% (95% CI, 93-100), 97.1% (95% CI, 85-100), 100% (95% CI, 95-100) and 0.98 for RFM, 97.1% (95% CI, 85-100) ,96.1% (95%, 89-99), 91.7% (95% CI, 78-98), 98.7% ((95% CI, 93-100) and 0.92 for SM and 100% (95% CI, 88-100), 97.7% (95% CI, 91-100), 93.3% (95% CI, 78-99), 100% (95% CI, 95-100)and 0.93 for EMB.CONCLUSIONS: The results obtained by direct NRA demonstrated excellent concordance for all drugs. Direct NRA is an assay which detects DR-TB directly from sputum rapidly and has the potential to become an alternative to existing methods particularly in resource-poor settings

Evaluation of nitrate reductase assay in 7H11 agar for diagnosis of multi-drug-resistant tuberculosis in eastern Nepal

“…The results by NRA were obtained much earlier (19.3 days) than the conventional PM (72 days) where majority (82.7%) of the positive results was available within 21 days. In contrast to our results, Satti et al and Lamsal et al have reported high sensitivity of 100% for RIF and more than 97% for INH [ 9 , 16 ]. However, our findings were consistent with the results of majority of the studies where NRA was done directly on sputum samples [ 17 – 19 ].…”

Knowledge, attitudes and practices relating to antibiotic use among community members of the Rupandehi District in Nepal

“…This paper reports on research that explores the knowledge, attitudes and practices of community members in relation to antibiotic use in the Rupandehi district in Nepal. Previous studies in Nepal have investigated surgical site infection and antibiotic use [29], antibiotic resistance [30–33], antibiotic prescribing and sensitivity [34], antibiotic prescribing patterns [35, 36], antibiotic dispensing practices [37], knowledge, attitudes and practices of medical students in relation to antibiotics use [38], and dispensing practices and patients’ knowledge about drug use [39]. However, to our knowledge no population based studies have been conducted on knowledge, attitudes and practices relating to antibiotics use.…”

Comparative evaluation of nitrate reductase assay with conventional proportion method for isoniazid and rifampicin susceptibility testing in smear positive pulmonary tuberculosis patients

“…14 Hence it is important to know the resistant to RIF. Our study is in complete concordance with the studies using direct nitrate reductase assay for drug susceptibility testing of M. tuberculosis conducted by.Affolabi et al, 12 Mishra et al, 15 Thapa et al 16 In resource-constraint areas cost is an imperative aspect where most of the disease is prevalent. A cost by NRA as compared with PM and molecular assays accentuates the need of this colorimetric assay to be routinely used in laboratories in low-income countries.…”