Assessment of line probe assay for rapid detection of extensively drug-resistant Mycobacterium tuberculosis isolates

Aims and objectives: Molecular techniques have considerable advantages for rapid detection, a reduction of infectiousness, prevention of further resistance development and surveillance of drug-resistant TB. MTBDRsl VER 2.0 was used to detect resistance to second-line anti-tuberculosis drugs on rifampicin-resistant M. tuberculosis (RR-MTB) isolates compared to the minimum inhibitory concentrations (MICs) and whole genome sequencing (WGS). Methods: The MTBDRsl VER 2.0 (Hain Life Science, Nehren, Germany) and WGS (San Diego, CA, USA) was performed for tracing mutations in resistant-related genes involved in resistance to fluoroquinolone (FLQs) and second-line injectable drugs (SLIDs). The broth microdilution method using 7H9 Middlebrook media supplemented with OADC was used to determine the MICs. Results: The MTBDRsl VER 2.0 correctly detected 5/6 (83.3%) of FLQ-resistant strains having gyrA mutations. The MUT1 A1401G (7 strains) and MUT2 G1484T (1 strain) mutations in rrs gene were detected in 8 AMK/KAN/CAP-resistant strains. Four low-level KAN-resistant strains with the G-10A/C-12T (3 strains) and C-14T (1 strain) mutations in eis gene was diagnosed using MTBDRsl VER 2.0. Conclusions: Five error results were found in detecting resistance to kanamycin and capreomycin compared to the phenotypic drug susceptibility testing and WGS. Failing wild type-bands without improved mutant-bands did not indicate a reliable resistance. WGS could efficiently resolve the discrepancies of the results. MTBDRsl showed better performance in detecting extensively drug-resistant strains.