[Identification of 23 mycobacterial species by Invader assay with targeting 16S rRNA gene and ITS-1 region--comparison with DDH method in clinical isolates].

PURPOSE AND METHOD The Invader assay was developed to identify 23 mycobacterial species using probes derived from the species-specific region of the 16S rRNA gene and the 16S-23S rRNA internal transcribed spacer 1 (ITS-1) region, with minor modifications of our previous study. In the present study, we compared the identification capability between the Invader assay and DNA-DNA hybridization (DDH) method. DDH is commonly used to identify non-tuberculosis mycobacterium in Japan and 636 clinical mycobacterial strains cultured on Ogawa slants were tested. RESULTS The Invader assay could identify 615 (96.7%) of the 636 strains. The results contained 14 M.lentiflavum, 3 M. parascrofulaceum and 1 M. intermedium, which were undetectable with DDH method. On the other hand, DDH method could identify 580 (91.2%) strains with duplicate assay. Of 628 strains except 8 strains identified as a few species by Invader assay, 551 (87.7%) strains were identified as the same species by two methods. Discordant results were mainly recognized for the identification of M. gordonae, M. avium, M. lentiflavum and M. intracellurare. The results of other methods targeting 16S rRNA indicated correctness of the Invader assay. CONCLUSION These results indicate that Invader assay could identify more correctly than DDH method and could identify about 97% of clinically important mycobacterium.