Description of sp. nov

In the November 2000 issue of the Journal of Clinical Microbiology, Roth et al. (1) presented a paper with the description of a new Mycobacterium species,Mycobacterium heckeshornense, based on multiple isolation of this species from one patient. Analyses of the biochemical and growth properties of their strain revealed an obviously close relationship toM. xenopi, with only three negative biochemical test results (arylsulfatase, nicotinamidase, and pyrazinamidase activities) discriminating this strain from M. xenopi. However, we analyzed two strains with the identical 16S rRNA gene sequence (GenBank accession number AJ243481 ; sequence submitted 28 June 1999 [http://www.ncbi.nlm.nih.gov/ ]) and found that the results for these three tests were clearly positive, as they were for M. xenopi. Thus, it seems that these properties may vary among clinical isolates of M. heckeshornense and cannot conclusively be used to differentiate it from M. xenopi. These results once more emphasize that the description of a new species should be based on a minimum number of strains, e.g., 5 to 10 strains.