Phylogenetic analysis of Mycobacterium aurum and Mycobacterium neoaurum with redescription of M. aurum culture collection strains.

We examined American Type Culture Collection (ATCC) strains of Mycobacterium aurum and Mycobacterium neoaurum by using multilocus DNA target sequencing. Apart from the type strain, all 10 ATCC M. aurum strains examined were classified incorrectly, with most being reclassified as belonging to the M. neoaurum-'Mycobacterium lacticola' relatedness group. All four M. neoaurum strains were tightly clustered, but heterogeneity was observed within the cluster. As a result of the incorrect annotation of the M. aurum strains, two commonly used methods of identification are compromised and two case reports implicating M. aurum as a human pathogen are probably incorrect, with the isolates probably belonging to the M. neoaurum-'M. lacticola' relatedness group. These findings together with a review of isolates identified at two large reference laboratories suggest that M. aurum is not a clinically significant isolate.