Comparative evaluation of Anyplex II MTB/MDR/XDR and resazurin microtiter assay for detection of drug resistant Mycobacterium tuberculosis

Abstract

Drug-resistant (DR) tuberculosis (TB) is a persistent threat and presents the main challenge for TB control programs. Rapid diagnosis is essential for controlling drug-resistant cases. The aim of the study was to evaluate the performance of multiplex real-time PCR assay using Anyplex II MTB/MDR/XDR (Anyplex) kit to detect DR-TB and its concordance with Resazurin microtiter assay (REMA). The susceptibility of Mycobacterium tuberculosis, to isoniazid (INH), rifampicin (RIF), ofloxacin (OFX), and kanamycin (KAN), was evaluated by using REMA and Anyplex kit with 32 drug-resistant TB and 18 susceptible strains. Proportion method was used as gold standard. All susceptible strains were susceptible to REMA and Anyplex methods. Anyplex and REMA identified 75% and 85% of the multidrug-resistant (MDR)-TB isolates, respectively. The sensitivity of the REMA assay as compared to PM was 96.4 %, 90.9%, 85.7%, and 100%, respectively, for INH, RIF, OFX, and KAN, whereas the sensitivity of Anyplex was78.5 %, 77.2%, and 85.7% for INH, RIF, and OFX, respectively. The agreement between Anyplex and REMA was relative to INH, RIF, and OFX (kappa scores, k =0.8, 0.79 and 0.83 respectively). There was no isolate identified as KAN resistant by Anyplex. REMA, as a rapid phenotypic method, is suggested for detecting drug-resistant TB isolates that have not been detected by the Anyplex method.