Identification of an insertion sequence-like element in a subspecies of Mycobacterium kansasii

Analysis of a genomic DNA clone library of a strain from the genetic subspecies of Mycobacterium kansasii determined the existence of a repetitive insertion sequence-like element. The element is 947 bp long and is present in a minimum of 1 to 11 copies per genome. Similar to insertion sequences, it contains a 3-bp (TAG) direct repeat at its extremities and a transcription promoter-like sequence. In addition, for one of the clones sequenced, a potential cointegrate formation, a characteristic frequently observed with insertion sequences, was revealed. This insertion sequence does not contain short inverted repeats near the ends or a large open reading frame to code for a transposase enzyme. Its host range is restricted to a previously described genetic subspecies of M. kansasii and is not present in typical M. kansasii or other mycobacterial species. When used as a probe for Southern blot hybridization, significant heterogeneity between different isolates of the M. kansasii subspecies was observed. This repeated element will be useful in further studies on the characterization, diagnosis, and epidemiology of M. kansasii.