“The other nontuberculous mycobacteria (NTM): Clinical aspects of lung disease caused by less common slow-growing NTM species”

Slow-growing nontuberculous mycobacteria (NTM) comprise a diverse group of environmental organisms, many of which are important human pathogens. The most common and well-known member of this group is Mycobacterium avium, the leading cause of nontuberculous mycobacterial pulmonary disease (NTM-PD) globally. This review focuses on the less common, but notable species of slow-growing NTM with respect to lung disease. To prepare this article, literature searches were performed using each species name as the keyword. Society guidelines were consulted, and relevant articles were also identified through the reference lists of key papers. The specific organisms highlighted include M. kansasii, M. xenopi, M. malmoense, M. simiae, and M. szulgai. While these organisms are closely related, they have distinct epidemiology and behaviour as pathogens. Therefore, the diagnosis and management of NTM-PD require a nuanced approach that takes into consideration the unique characteristics of each species. There is limited evidence to inform the optimal treatment of NTM-PD. Antimicrobial therapy is often challenging due to the presence of drug resistance and few antibiotic options. Regimen selection should generally be guided by drug susceptibility testing, although the correlation between clinical outcomes and in vitro susceptibility thresholds have not been defined for most species.