Mycobacterium toneyamaense sp. nov., a novel rapidly growing mycobacterium isolated from human patients.

A rapidly growing acid-fast bacterium not consistent with existing species had previously been isolated from an immunocompetent patient with chronic and progressive pulmonary disease. Herein, we aimed to further characterize five clinically isolated strains based on genetic and phenotypic examinations and propose a novel species. The 16S rRNA gene sequence of the five strains had 99.6-99.7% similarity with that of Mycobacterium mucogenicum and clustered most closely to M. mucogenicum in a phylogenetic analysis based on single-copy marker genes. The average nucleotide identity values of the strains against M. mucogenicum and Mycobacterium phocaicum were ≤93.6% and ≤93.2%, respectively, indicating that they are separate species. The strains formed smooth colonies within 3-4 days and grew at temperatures between 24 and 42 °C, with optimal growth at 37 °C. The biochemical characteristics of the novel species were similar to those of M. mucogenicum and M. phocaicum. It predominantly contained C16:0 and C18:1 (n-9cis) fatty acid and molecular species of mycolic acid, such as C77:2 and C79:2 of α-mycolic acids, C77:0 and C79:0 of keto-mycolic acids and C58:1 and C60:1 of dicarboxy-mycolic acids. Based on the genomic analyses, we propose a novel species, named Mycobacterium toneyamaense, with the type strain LRC2408T (=JCM 37957T=KCTC 59531T).