Four novel nontuberculous mycobacteria species: sp. nov., sp. nov., sp. nov. and sp. nov. revived from a historical Danish strain collection.

Four novel nontuberculous mycobacteria were discovered from a historical strain collection at the International Reference Laboratory of Mycobacteriology at Statens Serum Institut in Copenhagen, Denmark. Phylogenetic analysis combining the 16S , internal transcribed spacer and 23S elements, as well as a single-copy core-gene (, , and ) analysis of these freeze-dried mycobacteria, clinically isolated from gastric lavage samples between 1948 and 1955, showed to be associated with type strains grouping within the Terra and Fortuitum-Vaccae clade. Phenotypic characteristics, biochemical properties and fatty acid and mycolic acid profiles supported the classification as novel strains. A genomic comparison to the closest related type strain was done by calculating average nucleotide identity and DNA:DNA hybridization values, which showed 87.9% and 33.0% for Mu0050, 85.2% and 27.4% for Mu0053, 85.3% and 27.6% for Mu0083 and 93.3% and 50.1% for Mu0102, respectively. The names proposed for the new species are sp. nov. (Mu0050=ITM 501390=CCUG 77525), sp. nov. (Mu0053=ITM 501391=CCUG 77526), sp. nov. (Mu0083=ITM 501392=CCUG 77527) and sp. nov. (Mu0102=ITM 501393=CCUG 77528).