Molecular typing of Mycobacterium tuberculosis strains isolated from patients in Markazi Province

Background: RFLP-IS6110 standard technique to genotyping M. tuberculosis.The aims of this study were to identify the genetic diversity of M. tuberculosis population in Markazi province and to recognize the mode of disease transmission in this region. Material and Methods: The RFLP results of 42 isolates of M. tuberculosis deposited in the Mycobacterial Centre from Markazi province were analyzed. DNAs isolated from these isolates were enzyme digested with Pvu II, and hybridized with a PCR amplified DIG-labeled IS6110 probe. Results: The isolates were classified into four groups, based on the copy numbers, as follows: (1) lacking IS6110 element (2) low copy numbers (1-2) (3) intermediate copy numbers (3-5) and (4) high copy number (6-17). Copy numbers higher than 17 however were not observed in any of the isolates studied, 72 percent of the isolates showed high copy numbers of IS6110, 13 percent intermediate copy numbers, 10 percent low copy numbers, whereas 5 percent isolates lacked IS6110 element. Conclusion: IS6110 DNA fingerprinting assisted us to find epidemiological links between some TB cases, and this technique estimates from reactivation of latent infection transmission of the disease in Markazi province. The low rate of clustering indicates that tuberculosis among studied population is resulted mainly from reactivation of latent infection in this region.