Taxonomic and phylogenetic status of non-tuberculous mycobacteria in a Caribbean setting

This report describes detailed taxonomic and phylogenetic analysis of 15 non-tuberculous mycobacteria (NTMs) isolated from human pathological specimens in a Caribbean setting (12 slow-growers and three rapid-growers) that were not identified by cultural and biochemical tests and drug-susceptibility results. These isolates were further studied using PCR restriction fragment length polymorphism analysis (PRA) of a 441bp hsp65 fragment, as well as the sequencing of 16S rDNA and hsp65 DNA, and HPLC of the mycolic acids. Our results showed that taxonomic position of well-defined NTMs was resolved by PRA and sequencing of hsp65, nonetheless, it was not suitable to investigate rarely observed or new strains that required 16S rDNA sequencing and HPLC for a definite response. Unrooted neighbor-joining phylogenetic trees were drawn based upon the 16S rDNA and hsp65 sequences of the 15 NTMs compared with those from described species (73 for 16S rDNA and 45 for hsp65). For most of the NTMs not showing an exactly matching sequence with either hsp65 or 16S rDNA in the GenBank, the phylogenetic tree was able to provide with useful indications about their relatedness to known species. In such a case, a concording HPLC pattern with the sequence data and the place of the strain within the tree could lead to a potential identification. We also identified three identical isolates that define a new mycobacterial species within the group of M. simiae-related mycobacteria. The isolation and characterization of mycobacteria from new settings may lead to identify potential pathogens that may propogate in future because of increased human migration, travels, and climatic and ecological changes of the modern world.