Genomic and phenotypic characterization of Mycobacterium tuberculosis’ closest-related non-tuberculous mycobacteria

Abstract

In this work, we investigated recently identified opportunistic mycobacterial pathogens that are genomically more closely related to Mycobacterium tuberculosis ( Mtb ) than previously used comparator species Mycobacterium kansasii and Mycobacterium marinum . We confirmed that Mycobacterium decipiens is the currently closest known species to the tubercle bacilli, represented by Mycobacterium canettii and Mtb strains. Surprisingly, the reference strain of Mycobacterium riyadhense (DSM 45176), which was purchased as a biosafety level 1 (BSL-1)-rated organism, was the most virulent of the four species in the tested cellular and mouse infection models, suggesting that a BSL-2 rating might be more appropriate for this strain than the current BSL-1 rating. Our work establishes the four NTM species as interesting study models to obtain new insights into the evolutionary mechanisms and phenotypic particularities of mycobacterial pathogens that likely have also impacted the evolution of the key pathogen Mtb .