Evaluation of the Speed-oligo® Mycobacteria assay for identification of Mycobacterium spp. from fresh liquid and solid cultures of human clinical samples

We evaluated the ability of a novel DNA strip assay (Speed-oligo® Mycobacteria) to differentiate mycobacterial species. It is based on polymerase chain reaction targeting 16S rRNA and 16S-23S rRNA regions and double-reverse hybridization on a dipstick using probes bound to colloidal gold and to the membrane. We blindly tested its capacity to identify 182 acid-fast bacilli grown on fresh liquid (BacT/Alert, MGIT) and solid (Lowenstein–Jensen) cultures (from Spanish mycobacteriology laboratories), previously identified by means of Genotype® Mycob.CM/AS or Gen-Probe® AccuprobeMTC, and 11 collection strains of mycobacteria-related organisms. Discrepancies were resolved by 16S rRNA sequencing. Results were interpreted by identification of 7 specific bands for the following: Mycobacterium sp., M. fortuitum, Mycobacterium avium–intracellulare complex, Mycobacterium tuberculosis complex, Mycobacterium kansasii, M. gordonae, and M. abscessus–chelonae complex. No cross-reactivity was observed with any mycobacteria-related organism. Concordant results were obtained for 177/182 bacilli (97.2%). There was only 1 major discrepancy, misidentification of Mycobacterium marinum as M. kansasii, verified by sequencing.