Distribution of Nontuberculous Mycobacteria by Multigene Sequence-Based Typing and Clinical Significance of Isolated Strains

Abstract

bSpecies 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.A ll members of the genus Mycobacterium, excepting M. tuberculosis and M. leprae, are considered nontuberculous mycobacteria (NTM) and are frequently isolated from environmental sources, including surface or tap water and soil (1). Currently, more than 160 mycobacterial species/subspecies are listed in the Genus Mycobacterium database (http://www.bacterio.cict.fr/m /mycobacterium.html; accessed on 22 August 2013), and the number of newly identified NTM is increasing. Recent data suggest that the incidence of lung disease caused by NTM with or without predisposing risk factors has been growing worldwide (2-6). However, epidemiologic data on the distribution and clinical significance of NTM lung disease are still scarce because NTM lung disease is not a reportable condition in most countries.In South Korea, NTM was first described as a cause of mycobacterial lung disease in 1981 (7); since then, the frequency of isolation of NTM from clinical specimens has shown a continuous increase. Since the 2000s, the frequency of NTM isolation has been reported to be 12 to 38% of mycobacterial culture-positive specimens, and the number of patients with NTM disease has also been considerable, with a frequency of 8 to 49% of isolated NTM (8-15). The isolation of NTM species from respiratory specimens is not sufficient evidence for the diagnosis of clinically significant NTM lung disease, since there are also clinical, radiographic, and microbiological criteria (1).Recently, various genotype-based methods for the identification of NTM have been developed to ra...

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Clonal Diversification and Changes in Lipid Traits and Colony Morphology in Mycobacterium abscessus Clinical Isolates

“…In the United States and some other parts of the world, it is the second most frequent pulmonary nontuberculous mycobacterial (NTM) infection (28%), after Mycobacterium avium complex, and its prevalence is increasing (6,7). MABSC causes significant mortality in the CF population.…”

Treatment of Non-Tuberculous Mycobacterial Lung Disease

“…Newer molecular techniques that allow more precise identification include line probe hybridization and PCR. For the most precise identification of NTM species and subspecies, sequencing of hsp65 and rpoB genes, as well as the 16S-23S ITS is recommended (19–23). Furthermore, the infrequent use of NTM genotyping in the clinical setting makes it difficult to ascertain whether recurrent disease is due to a relapse or a new infection acquired from the environment.…”