Comparison of mycobacterial interspersed repetitive unit-variable number tandem repeat and IS6110-RFLP methods in identifying epidemiological links in patients with tuberculosis in Northwest of Iran

In recent years in spite of medical advancement, tuberculosis remains as a worldwide health problem. Therefore, identifying the source of transmission of infection is necessary for decreasing of tuberculosis (TB), also determining the varieties of TB strains by DNA fingerprinting helps to achieve this objective. The aim of present study was to determine tuberculosis transmission dynamics in Northwest of Iran with MIRU-VNTR and IS6110-RFLP methods. MIRU-VNTR performed for analysis of 125 strains and restriction fragment length polymorphism (RFLP) typing was performed on 119 culture-positive specimens during a period of September 2002 to March 2003 in tuberculosis centres of the region. We found 93 distinct MIRU-VNTR patterns, including in 21 clustered patterns and 72 unique patterns from isolated strains. The discriminatory power of MIRU-VNTR typing in our study was high (Hunter-Gaston discriminatory index, HGDI = 0.9932) for isolates. Ninety-three distinct IS6110 patterns were revealed. Twelve clusters were found among total of 38 strains. The clusters included 26 patients who infected by 12 another's. HGDI for our IS6110-RFLP method was 0.9928. The minimum estimate for the proportion of tuberculosis that was due to transmission with IS6110-RFLP was 21.9% and with MIRU-VNTR was 26.4%. In clusters the same patterns of Nakhichevanees patients and Iranian patients were revealed in three clusters with MIRU-VNTR and one cluster in IS6110 which showed that Nakhichevanees patients referred to tuberculosis centres of province could be a source of tuberculosis transmission. RFLP typing has more discriminatory power and it can be concluded that this method is a useful instrument for the better understanding of transmission and the occurrence of micro-epidemics and source tracing.