International Journal of Science and Research (IJSR) ISSN: 2319-7064 Impact Factor (2018): 7.426 Volume 8 Issue 3, March 2019 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Evaluation of Direct Nitrate Reductase Assay for Drug Susceptibility Testing of Mycobacterium tuberculosis in Resource - Poor Settings Olubunmi Alaka 1 , Anuoluwapo Alaka 2 , Olamide Agboola 3 , Augusta Onuoha 4 1 Department of Medical Microbiology and Parasitology, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria 2 Department of Chemical Pathology, Ladoke Akintola University of Technology, Ogbomoso, Nigeria 3 International Organization for Migration, Lagos, Nigeria 4 Department of Medical Microbiology and Parasitology, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria Abstract: Direct Nitrate Reductase Assay (DNRA) was used for susceptibility testing of Mycobacterium tuberculosis to two front line anti-tuberculosis drugs (Rifampicin and Isoniacid) from 100 Acid fast bacilli smear-positive sputum samples. The DNRA results were compared with the gold standard conventional proportion method (PM). Ninety eight (98) sputum specimens result were comparable with the gold standard. DNRA results were obtained at day 10 for 72 specimens, results for 17 specimens were obtained at day 14, and the results for 9 specimens were obtained at day 18. Thus, 74% of DNRA results were obtained in 10 days. The sensitivities and specificities of DNRA were 100%, 97% and 100%, 99% for Rifampicin and Isoniacid respectively. Positive predictive values were 100% and 93% for Rifampicin and INH respectively while negative predictive values were 97% and 100% for Rifampicin and Isoniacid respectively. NRA has been demonstrated as rapid, accurate, and cost-effective method for drug susceptibility testing of Mycobacterium tuberculosis. Therefore, NRA constitutes a useful tool for detection of tuberculosis drug resistance in low-resource countries. Keywords: Mycobacterium tuberculosis, Drug testing, Nitrate Reductase Assay 1. Introduction Tuberculosis (TB), an infectious bacterial disease with significant morbidity and mortality, is the leading cause of death in the world from a bacterial infections. The aetiological agent of TB is the group of Mycobacterium tuberculosis complex comprising of Mycobacterium tuberculosis, M. bovis, M. africanum, M.microti, M. canettii, M. caprae, M. pinnipedii, M. suricattae and M. mung [1]. TB was declared a global health emergency by the World Health Organization (WHO) in 1993 and claims approximately 1.7 million lives per annum, more than can be attributed to any other bacterial infection. It is estimated that one-third of the world’s population is infected with causative agent, obligate human pathogen M. tuberculosis, with around 9 to 10 million new cases of TB being reported each year [2]. Transmission of TB usually occurs by an airborne or aerosol but can also occur through the gastrointestinal tract and approximately 5 to 10 percent of cases overall are thought to result from spontaneous reactivation of latent TB infection [3]. Improved living standards and better sanitation led to a significant decrease in TB incident even before advent of effective TB chemotherapy. The introduction of TB chemotherapy in the mid-twentieth century made TB curable for the first time and further reduced TB incidence in industrialized countries. Despite the availability of the BCG (Bacilli Calmette - Guerin) vaccine and TB chemotherapy, the disease is on the increase in recent years largely due to HIV infection especially in poverty stricken regions and also to immigration, increased trade and globalization. The alarming increase of drug resistant TB, especially multi-drug resistant – TB (MDR - TB), (defined as resistant to at least two frontline TB drugs – isoniazid and rifampicin) and extensively drug-resistant TB (XDR-TB) (additional resistance to fluoroquinolone and one of injectable antibiotics) has caused a great deal of concern and becoming an increasing threat to the control of the disease in recent years. Early detection of drug resistance is key to the eradication of tuberculosis. The current methods for drug susceptibility testing (DST) of Mycobacterium tuberculosis are either costly or slow. As the prevalence of multidrug-resistant strains increases, there is need for fast, reliable, and inexpensive DST methods as against the traditional solid culture methods that can be applied in settings with scarce resources. Several approaches have been made for DST of TB. The relatively cheap traditional solid culture method is sensitive and specific but very slow (not less than 4weeks). The Microscopic Observation Drug Susceptibility (MODS) and Molecular methods are rapid, sensitive and specific but needs sophisticated equipment which are not readily available in resource poor settings [1]. Other susceptibility methods are still under evaluation and not yet available for commercial use. Therefore, the aforementioned short comings calls for the evaluation of an inexpensive Nitrate Reductase Assay (NRA) Paper ID: ART20195968 10.21275/ART20195968 635