Routine identification of Mycobacterium tuberculosis complex isolates by automated hybridization

Methodologies for biochemical identification of mycobacteria isolated from clinical samples are still cumbersome, taking skilled technicians 3 to 6 weeks. We describe here a 2-h identification system for mycobacterial isolates belonging to the Mycobacterium tuberculosis complex using a DNA probe. After 30 min of hands-off sample preparation, the 1.5-h hybridization test is totally automated in the newly developed VIDAS system (bioMérieux, Marcyl'Etoile, France), which performs solid-phase specific hybridization of 16S rRNA at 37 degrees C. The strain collection of actinomycetes tested was composed of 662 isolates from 27 species: 461 members of the M. tuberculosis complex (443 M. tuberculosis, 10 M. bovis, and 8 M. bovis BCG isolates) and 201 isolates of other species, including 55 M. avium-intracellulare isolates). They were identified by traditional methods: growth rate, colonial morphology, pigmentation, and biochemical profiles. The automated probe assay displayed an excellent correlation with the reference results. The four members of the Nocardia and Rhodococcus genera tested did not cross-hybridize. This flexible random-access and automated technology was shown to suit the routine context of the laboratory by rapidly delivering the results.