Nature of DNA polymorphism in the direct repeat cluster of Mycobacterium tuberculosis; application for strain differentiation by a novel typing method

Mol Microbiol. 1993 Dec;10(5):1057-65. doi: 10.1111/j.1365-2958.1993.tb00976.x.


Mycobacterium tuberculosis complex strains contain a unique chromosomal region, which consists of multiple 36bp direct repeats (DRs), which are interspersed by unique spacers 35 to 41 bp in length. In this study we investigated the nature of the DNA polymorphism of this DR cluster by sequencing part of this region in a large number of M. tuberculosis complex strains. Two types of genetic rearrangements were observed. One type consists of the variation in one or a few discrete, contiguous DRs plus spacer sequences. This variation is probably driven by homologous recombination between adjacent or distant DRs. The other type of polymorphism is probably driven by transpositional events of the insertion sequence, IS6110, which is almost invariably present in the DR cluster of M. tuberculosis complex strains. Based on the nature of the DNA polymorphism in the DR cluster, we developed a novel method of strain differentiation, direct variable repeat polymer chain reaction (DVR-PCR), which enables typing of individual M. tuberculosis strains in a single PCR. The method allows an excellent differentiation of epidemiologically unrelated isolates and, in principle, the DVR-PCR allows the detection of M. tuberculosis and strain differentiation at the same time.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Typing Techniques*
  • Base Sequence
  • DNA Primers / genetics
  • DNA Transposable Elements / genetics
  • DNA, Bacterial / genetics
  • DNA, Ribosomal / genetics
  • Gene Rearrangement
  • Genetic Variation
  • Molecular Sequence Data
  • Mycobacterium bovis / genetics
  • Mycobacterium tuberculosis / classification
  • Mycobacterium tuberculosis / genetics*
  • Oligonucleotide Probes / genetics
  • Polymerase Chain Reaction / methods
  • Polymorphism, Genetic*
  • Recombination, Genetic
  • Repetitive Sequences, Nucleic Acid*
  • Species Specificity


  • DNA Primers
  • DNA Transposable Elements
  • DNA, Bacterial
  • DNA, Ribosomal
  • Oligonucleotide Probes