Molecular Detection of Drug resistant and Non Tuberculosis Mycobacteria using Line Probe Assay: A case study from North India

Abstract

Growing concerns about the spread of multidrug-resistant tuberculosis (MDR-TB) and the emergence of extensively drug-resistant TB have triggered substantial interest in the development and application of rapid tests for the detection of drug-resistant TB. Molecular assays to detect gene mutations that signal drug resistance are widely recognized as being most suited for rapid diagnosis. Among molecular assays, line probe assays (LPA) have shown great promise. In this study, we have tested eight hundred thirty smear positive sputum samples by LPA for the presence of M. tuberculosis complex and resistance to isoniazid and rifampicin as per the diagnostic mandate of an accredited reference laboratory. As per the mandate, samples that were positive for M. tuberculosis complex were cultured, and then again tested by LPA. A retrospective analysis of the results was carried out. M. tuberculosis complex could be detected in 797 (96.02%) but not in 33 (3.9%) of smear-positive sputum samples. Of the 797 positive samples, 24 (3.0%) were MDR, 6 (0.75%) were rifampicin mono-resistant and 33(4.1%) were INH mono-resistant. LPAs have a continued role for use in settings where rapid identification of INH resistance and clinically relevant NTM are priorities.