Abstract
We evaluated the GenoType NTM-DR (NTM-DR) line probe assay for identifying Mycobacterium avium complex (MAC) species and Mycobacterium abscessus subspecies and for determining clarithromycin and amikacin resistance. Thirty-eight reference strains and 145 clinical isolates (58 MAC and 87 M. abscessus isolates), including 54 clarithromycin- and/or amikacin-resistant strains, were involved. The performance of the NTM-DR assay in rapid identification was evaluated by comparison with results of multigene sequence-based typing, whereas performance in rapid detection of clarithromycin and amikacin resistance was evaluated by comparison with sequencing of the erm(41), rrl, and rrs genes and drug susceptibility testing (DST). The accuracies of MAC and M. abscessus (sub)species identification were 92.1% (35/38) and 100% (145/145) for the 38 reference strains and 145 clinical isolates, respectively. Three MAC strains other than M. intracellulare were found to cross-react with the M. intracellulare probe in the assay. Regarding clarithromycin resistance, NTM-DR detected rrl mutations in 52 isolates and yielded 99.3% (144/145) and 98.6% (143/145) concordant results with sequencing and DST, respectively. NTM-DR sensitivity and specificity in the detection of clarithromycin resistance were 96.3% (52/54) and 100% (91/91), respectively. The NTM-DR yielded accurate erm(41) genotype results for all 87 M. abscessus isolates. Regarding amikacin resistance, NTM-DR detected rrs mutations in five isolates and yielded 99.3% (144/145) and 97.9% (142/145) concordant results with sequencing and DST, respectively. Our results indicate that the NTM-DR assay is a straightforward and accurate approach for discriminating MAC and M. abscessus (sub)species and for detecting clarithromycin and amikacin resistance mutations and that it is a useful tool in the clinical setting.