Distribution of nontuberculous mycobacteria by multigene sequence-based typing and clinical significance of isolated strains

Abstract

Species identification of nontuberculous mycobacteria (NTM) is challenging due to the increasing number of identified NTM species and the lack of standardized testing strategies. The objectives of this study were to investigate the distribution of NTM species recovered from respiratory specimens by multigene sequence-based typing and to evaluate the clinical significance of identified species. Two hundred thirty-two consecutive clinical NTM isolates were subjected to sequencing of multiple genes, including hsp65, rpoB, and 16S-23S rRNA internal transcribed spacer (ITS) sequence. In addition, clinical data from all patients whose specimens had NTM isolates were analyzed to examine clinical virulence and treatment history. Eighteen strains from 227 isolates from 169 patients were successfully identified at the species level by multigene sequence-based typing. Mycobacterium avium complex and M. abscessus complex made up the majority of isolated NTM (88%; 199/227), followed by M. fortuitum complex (4%; 10/227). The pathogenic potential of NTM differs enormously by species, and M. avium complex and M. abscessus complex revealed especially high levels of virulence compared with findings for other NTM species. The results from our work support M. avium complex and M. abscessus complex being the most common NTM species with highly pathogenic potential isolated from clinical respiratory specimens and could be a good resource for molecular epidemiology of NTM species in South Korea.

FIG 1

Schematic representation of detection ranges for NTM species by commercial assays. The expected detection coverage was calculated based on the proportions given for the identified NTM species for which data on multigene sequence-based typing were available. Other NTM species, which consisted of rarely isolated organisms (less than 2%), include M. nebraskense, M. marseillense, M. colombiense, M. porcinum, and M. senuense. The following DNA strip technology was used: AccuProbe (Gen-Probe, San Diego, CA), INNO-LiPA (Fujirebio, Ghent, Belgium), GenoType (Hain Lifescience GmbH, Nehren, Germany), and REBA Myco-ID (YD Diagnostics, Yongin, Republic of Korea). PCR-RFLP was carried out using PRA Myco-ID (YD Diagnostics, Yongin, Republic of Korea).