Abstract
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 to M. 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 {type:entrez-nucleotide,attrs:{text:AJ243481,term_id:6688803,term_text:AJ243481}}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. A strong reason for regarding M. heckeshornense as a separate species is its unique 16S rRNA gene sequence. Using this sequence, the authors performed a similarity analysis that confirmed the close relationship to M. xenopi. Yet, in spite of this detailed analysis, the authors did not mention the entry (dated 25 October 1998) in the GenBank database of a sequence with the accession number {type:entrez-nucleotide,attrs:{text:AF101243,term_id:9313049,term_text:AF101243}}AF101243 (http://www.ncbi.nlm.nih.gov/). Within the above-mentioned file a 249-bp fragment of the 5′ region of the ribosomal 16S rRNA, having a sequence identical to that of the now newly described species M. heckeshornense, was deposited and named M. sydneyiensis. This fragment comprised one part (region A, according to the paper of Roth et al. [1]) of the signature sequences that are widely used for mycobacterial species identification. It is well known to the authors of this letter that determination of only region A is not sufficient for species identification. However, the existence of an identical sequence within this region should have caused strong suspicion that the same species was under examination and should at least have been discussed in a paper aimed at the description of a new taxon. As of 24 July 2000, the entry {type:entrez-nucleotide,attrs:{text:AF101243,term_id:9313049,term_text:AF101243}}AF101243 has contained the complete 16S rRNA, which is 100% identical to the sequence of M. heckeshornense.
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