Characterization of a major polymorphic tandem repeat in Mycobacterium tuberculosis and its potential use in the epidemiology of Mycobacterium kansasii and Mycobacterium gordonae.

In this study, the occurrence of repeated DNA sequences in the chromosome of Mycobacterium tuberculosis was investigated systematically. By screening a M. tuberculosis lambda gt-11 gene library with labeled total chromosomal DNA, five strongly hybridizing recombinants were selected, and these contained DNA sequences that were present in multiple copies in the chromosome of M. tuberculosis. These recombinants all contained repeated sequences belonging to a single family of repetitive DNA, which shares homology with a previously described repeated sequence present in recombinant pPH7301. Sequences analysis of pPH7301 showed the presence of a 10-bp sequence that was tandemly repeated and invariably separated by 5-bp unique spacer sequences. Southern blot analysis revealed that the majority of the repeated DNA in M. tuberculosis is composed of this family of repetitive DNA. Because the 10-bp repeats are slightly heterogeneous in sequence, we designated this DNA as a major polymorphic tandem repeat, MPTR. The presence of this repeated sequence in various other mycobacterial species was investigated. Among the MPTR-containing mycobacterial species the chromosomal location of the repetitive DNA is highly variable. The potential use of this polymorphism in the epidemiology of mycobacterioses is discussed.