Identification of Mycobacterium kansasii by using a DNA probe (AccuProbe) and molecular techniques

The newly formulated Mycobacterium kansasii AccuProbe was evaluated, and th e results obtained with the new version were compared to the results obtain ed with the old version of this test by using 116 M. kansasii strains, 1 My cobacterium gastri strain, and 19 strains of several mycobacterial species. The sensitivity of this new formulation was 97.4% and the specificity was 100%. Still, three M. kansasii strains were missed by this probe. To evalua te the variability within the species, genetic analyses of the hsp65 gene, the spacer sequence between the 16S and 23S rRNA genes, and the 16S rRNA ge ne of several 116 M. kansasii AccuProbe-positive strains as well as all Acc uProbe-negative strains were performed. Genetic analyses of the one M. gast ri strain from the comparative assay and of two further M. gastri strains w ere included because of the identity of the 16S rRNA gene in M. gastri to t hat in M. kansasii. The data confirmed the genetic heterogeneity of M. kans asii. Furthermore, a subspecies with an unpublished hsp65 restriction patte rn and spacer sequence was described. The genetic data indicate that all il l; kansasii strains missed by the AccuProbe test belong to one subspecies, the newly described subspecies VL, as determined by the hsp65 restriction p attern and the spacer sequence. Since the M. kansasii strains that are miss ed are rare and all M. gastri strains are correctly negative, the new formu lated AccuProbe provides a useful tool for the identification of M. kansasi i.