TRANSMISSION PATTERN OF TUBERCULOSIS USING RFLP-BASED IS6110

Background-The aim of this study was to determine IS6110 banding pattern of Mycobacterium tuberculosis (MTB) isolates for evaluation of tuberculosis (TB) transmission. These isolates were obtained from intermediate laboratories of six major provinces of Iran; East Azarbaijan, West Azarbaijan, Khorasan, Kerman, Kermanshah and Fars. Methods-Restriction fragment length polymorphism (RFLP) was performed on 100 suitable isolates, which have been obtained from some laboratories thought Iran. Fingerprinting was done using the oligonucleotide 6110 a’ (5΄-GTGAGGGCATCGAGGTGGC) and 6110 b΄ (5΄-GCGTAGGCGTCGGTGACAAA) primers. Results-We observed two types of banding patterns among the typed strains: sixty-two percent of MTB strains had a high copy number of IS6110, whereas 33% had a low copy number. In addition, five MTB strains (5%) without any IS6110 banding pattern were detected. The analysis of banding pattern in MTB isolates revealed heterogeneous DNA fingerprinting. The computer-assisted dendogram system demonstrated 8% to 51% similarity among typed strains. According to the available data, similarity between 90% and 100% is considered as homogeneous DNA fingerprinting. Conclusion-Since two banding patterns (low and high) have been detected, it could be suggested that two or more lineage for TB strains might exist in Iran, which requires further analysis. This study also suggests that in these cases, tuberculosis is characterized by the absence of obvious focuses of transmission.