Background:Mycobacterium tuberculosis genotyping can effectively improve tuberculosis (TB) control programs by controlling disease transmission. Pulsed field gel electrophoresis (PFGE) is a particularly powerful tool for determination of clonal identity of bacteria providing information for understanding and controlling the spread of disease.Objectives:The aim of present study was to investigate the genetic diversity of M. tuberculosis strains in Khuzestan province by the PFGE technique.Patients and Methods:In total, 80 M. tuberculosis positive cultures were obtained from tuberculosis patients. PFGE was performed on 60 PCR-confirmed isolates by using DraI and XbaI restriction enzymes according to standard protocols. Plugs containing digested DNA were then loaded on agarose gels and run using contour-clamped homogenous electric fields.Results:Fifty distinct DNA banding patterns were obtained by digestion of DNA with DraI and 38 DNA banding patterns by digestion with XbaI restriction enzymes. The patterns comprised of 17 different clusters in which cluster I was the major one, containing six strains. Three clusters contained three strains each and the 13 remaining clusters comprised of two strains each. Digestion with DraI yielded 15-20 DNA fragments with 50-485 kb size, while digestion by XbaI produced DNA fragments with a size smaller than 50-242 kb.Conclusions:Despite the ability of PFGE for study of genetic diversity of many mycobacterial species and it being considered as a robust and useful tool, in this study we only found a 15% epidemiological relationship amongst the isolates. Thus, for higher discrimination of genotypic clusters among M. tuberculosis clinical isolates, the application of more sophisticated complementary techniques is required.

To investigate the genetic diversity of Mycobacterium tuberculosis (MTB) strains MIRU-VNTR as a powerful tool was used. In this study 80 isolates from patients were analyzed using primers based on IS6110 gene fragment specific for MTB complex. Then RD typing based on regions of difference was used to differentiate MTBC members. The MTB isolates were genotyped by 12 loci based MIRU-VNTR. The discriminatory index for each loci was calculated using the Hunter Gaston Discriminatory Index (HGDI).Of these, 60 cases were identified as MTB by polymerase chain reaction (PCR) method and RD-PCR typing. Forty eight distinct patterns comprising of 11 clusters and 37 unique Patterns were identified. The discriminatory power of MIRU-VNTR typing was high (HGDI= 0.991) for these samples. Also we could detect a case of mixed infection by MIRU-VNTR. The results show that MIRU-VNTR typing is a useful method for studying genetic diversity of MTB in regional settings.