RD7 genotyping of Mycobacterium tuberculosis strains isolated from patients with lung tuberculosis in various areas of Kazakhstan

A three-primer PCR assay has been designed for detecting possible deletions in the RD7 chromosomal region of the Mycobacterium tuberculosis complex. The assay gives rise to amplicons of different sizes depending on the presence or absence of deletions. The PCR assay was applied to 176 isolates from lung tuberculosis cases collected in various areas of Kazakhstan in the summer of 2004. Prior to assay, the isolates were characterized by culture and biochemical tests. The RD7 genotyping showed neither polymorphism nor deletions in the RD7 genome region. Some strains were additionally characterized by a PCR-RFLP analysis of the gyrB and hsp64 genes. The RFLP patterns corresponded to M. tuberculosis. The results of the study were consistent with certain previous studies, which indicates the population stability of RD7 in M. tuberculosis strains. Species identification of the isolates showed that M. tuberculosis sensu stricto was the principal causative agent of human lung tuberculosis in Kazakhstan.