Sequence analysis in the 23S rDNA region of Mycobacterium tuberculosis and related species

We sequenced a 516 base pair segment in the 23S rRNA gene of 54 Mycobacterium tuberculosis isolates, 52 of which were clinical isolates from Ethiopia. Sequence polymorphism was observed with 19 of the 54 strains; the polymorphic sites occurred in less than 2% (9/516) of the total sequence positions. The sequence variations represented base pair substitutions (14/23), insertions (9/23) or both (1/23). Insertions occurred at one site only, whereas substitutions were observed in various regions of the gene. There was no relation between mutational sites and drug susceptibility. However, using information from the GenBank database, comparison between the 23S rDNA sequences of M. tuberculosis and the corresponding sequences of other mycobacteria and of related non-mycobacterial species revealed considerable variation, suggesting that this region may provide a target for rapid detection and identification of mycobacteria both at the genus or species level.