UCLA

Mycobacterium abscessus infections are an emerging health care concern in patients with chronic pulmonary diseases, leading to high morbidity and mortality. One major challenge is resistance to clarithromycin, a cornerstone antibiotic with high efficacy. Therefore, treatment is primarily guided by phenotypic susceptibility results of clarithromycin, which requires extended incubation to assess for inducible resistance. Resistance mechanisms for clarithromycin include induction of erm(41) and mutations in the 23S rRNA gene (rrl). In addition, mutations in the 16S rRNA encoding gene (rrs) can confer high-level amikacin resistance, another essential drug in the treatment of M. abscessus infections. Herein, we developed a clinical whole genome sequencing (WGS) assay for clarithromycin resistance based on rrl and erm(41) gene sequences and amikacin resistance based on the rrs sequence in M. abscessus, as well as subspecies identification. Genotypic-based predictions were determined for 104 isolates from 68 patients. The overall accuracy of genotypic prediction for clarithromycin compared with phenotypic susceptibility results was 100% (95% CI, 96.45%-100%). For amikacin, we also obtained 100% accuracy (95% CI, 96.52%-100%). The high concordance between the genotypic and phenotypic results demonstrates that a WGS-based assay can be used in a clinical laboratory for determining resistance to clarithromycin and amikacin in M. abscessus isolates. WGS can also provide subspecies identification and high-definition phylogenetic information for more accurate M. abscessus strain typing.