Mycobacterium europaeum sp. nov., a scotochromogenic species related to the Mycobacterium simiae complex Four strains isolated in the last 15 years were revealed to be identical in their 16S rRNA gene sequences to MCRO19, the sequence of which was deposited in GenBank in 1995. In a polyphasic analysis including phenotypic and genotypic features, the five strains (including MCRO19), which had been isolated in four European countries, turned out to represent a unique taxonomic entity. They are scotochromogenic slow growers and are genetically related to the group that included Mycobacterium simiae and 15 other species. The novel species Mycobacterium europaeum sp. nov. is proposed to accommodate these five strains. Strain FI-95228 T (5DSM 45397 T 5CCUG 58464 T ) was chosen as the type strain. In addition, a thorough revision of the phenotypic and genotypic characters of the species related to M. simiae was conducted which leads us to suggest the denomination of the 'Mycobacterium simiae complex' for this group.A unique genetic signature characterizes a limited number of slowly growing non-tuberculous mycobacteria; it is represented by a 12 nt deletion in the 16S rRNA gene starting at Escherichia coli position 459. About 20 years ago, when genetic sequencing of the 16S rRNA gene began to be used for the taxonomic characterization of mycobacteria, Mycobacterium simiae appeared to be the only slowly growing mycobacterial species presenting the aforesaid deletion (Rogall et al., 1990; Kirschner et al., 1993b). Mycobacterium interjectum (Springer et al., 1993) was the first species to be newly described that was recognized to share this genetic marker with M. simiae and, in subsequent years, the group of M. simiae-like organisms has steadily extended and includes 16 species at present (Böttger et al., 1993;Fanti et al., 2004;Floyd et al., 1996Floyd et al., , 2000Haas et al., 1997;Karassova et al., 1965;Levi et al., 2003;Meier et al., 1993; Pourahmad et al., 2008;Selvarangan et al., 2004;Springer et al., 1993Springer et al., , 1996b