The respiratory microbiome and nontuberculous mycobacteria: an emerging concern in human health

Abstract

Nontuberculous mycobacteria (NTM) are diverse microbial species encompassing commensals and pathogens with the ability to cause pulmonary disease in both immunocompetent and immunocompromised individuals. In contrast to Mycobacterium tuberculosis, which has seen a reduction in disease rates in developed countries, the incidence and prevalence of NTM disease is increasing. NTM are difficult to treat with standard antimicrobial regimens and may contain both virulence and antibiotic-resistance genes with potential for pathogenicity. With the advent of molecular techniques, it has been elucidated that these organisms do not reside in isolation and are rather part of a complex milieu of microorganisms within the host lung microbiome. Over the last decade, studies have highlighted the impact of the microbiome on host immunity, metabolism and cell–cell communication. This recognition of a broader community raises the possibility that the microbiome may disrupt the balance between infection and disease. Additionally, NTM disease progression and antimicrobial therapy may affect the healthy steady state of the host and function of the microbiome, contributing to further dysbiosis and clinical deterioration. There have been limited studies assessing how NTM may influence the relationship between microbiome and host. In this review, we highlight available studies about NTM and the microbiome, postulate on virulence mechanisms by which these microorganisms communicate and discuss implications for treatment.

Clinical Characteristics and Mortality of Non-tuberculous Mycobacterial Infection in Immunocompromised vs. Immunocompetent Hosts

“…Non-tuberculous mycobacteria (NTM) include all species of mycobacteria except for M. tuberculosis and M. leprae and they are ubiquitous microorganisms that have an environmental origin. There are over 200 species of NTM identified to date, but only a few are pathogenic to susceptible hosts and are generally grouped with other opportunistic pathogens ( 1 , 2 ). The incidence and prevalence of NTM disease are increasing in some countries and regions, even surpassing the incidence and prevalence of tuberculosis ( 3 – 6 ).…”

Bad company? The pericardium microbiome in people investigated for tuberculosis pericarditis in an HIV-prevalent setting

“…The reasons for this are likely multifaceted: primarily due to technical methodological limitations (metagenomic sequencing would have more discriminatory power for species within Mycobacteria ) but could also be due to TB exposure, past infection, TB disease at another anatomical site, or cross-contamination. It is important to note that 66% of dTBs did not show Mycobacterium readings, likely due to the limited sensitivity of 16S rRNA sequencing for detecting this genus, whose cells often lyse and release DNA inefficiently and may be biased against by conventional sequencing approaches (a “mycobacteriome” approach could be used to study mycobacterial diversity further) 46 .…”

Mycobacterial Adhesion: From Hydrophobic to Receptor-Ligand Interactions

“…tuberculosis and M. leprae have historically been the most important mycobacterial pathogens, and their intracellular lifestyle may be seen as a paradigm of mycobacterial pathogenicity. Yet, several less important mycobacteria, causing mainly animal disease, and emerging pathogenic nontuberculous mycobacteria (NTM) appear to follow infective lifestyles that deviate from that of tuberculous and leprous bacilli, and, wherein, the mechanisms of adhesion are probably different [22,23]. Mycobacterium bovis, the causative agent of bovine tuberculosis, which can also cause zoonoses, can, in addition to an infection resembling pulmonary tuberculosis, cause gastrointestinal infections in humans after con-sumption of contaminated unpasteurized dairy products [24].…”