Mycobacterium sp. nov.

Five isolates of scotochromogenic slow-growing mycobacteria were obtained from sputum specimens of different patients in Japan between 2022 and 2024. Initial analysis using Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry failed to identify these isolates due to ambiguous results between Mycobacterium gordonae and Mycobacterium paragordonae. Subsequent whole-genome sequencing showed that these isolates were most closely related to M. paragordonae JCM 18565 but were clearly distinct, with average nucleotide identify values of 84.63-84.71%. Phenotypically, these isolates produced rough to occasionally smooth, yellow-orange colonies, and exhibited positive reactions for catalase activity and telluric acid reduction while showing negative results for nitrate reduction, arylsulfatase, and urease activities. Based on these distinct genomic and phenotypic characteristics, we propose these isolates represent a novel mycobacterium species.