Tuberculosis transmission in Northwest of Iran: using MIRU-VNTR, ETR-VNTR and IS6110-RFLP methods

Abstract

Tuberculosis is the main cause for adults' death from a single infectious agent killing about 2 million people every year. Identifying the source of transmission infection is necessary to decrease tuberculosis. In this study we used IS6110-RFLP, MIRU-VNTR and ETR-VNTR methods to determine transmission dynamic of tuberculosis in Northwest of Iran from March 2004 to March 2005. 156 culture positive isolates (51 from Orumieh and 105 from Tabriz) were collected. IS6110-RFLP was done by standardized method and MIRU-VNTR was done by 12 primers specific for 12 MIRU-VNTR loci by polymerase chain reaction and ETR was carried out by primers specific for ETR-A, ETR-B and ETR-C as well. Genetic relationship analyses were performed by MVSP software and MIRU-VNTRplus website. The results revealed that the copy number of IS6110 in isolates ranged from 0 to 17. One hundred and seven unique patterns and 16 shared patterns by 2-10 isolates were determined by IS6110-RFLP, and 116 distinct patterns were identified by MIRU-VNTR including 21 clustered patterns and 95 unique patterns. Having combined MIRU-VNTR and ETR-VNTR data, we increased the discriminatory power of typing method, thus 25 clusters were identified. Loci 10, 26, 40 in MIRU and ETR-A were highly discriminatory. Distribution of lineages in our study according to tentative data in MIRU-VNTRplus database was multi-matches 9.09%, Bovis 9.74%, S 8.44%, New-1 0.65%, Uganda I 0.65%, Haarlem 0.65%, Cameroon 0.65% and X 0.65%. The minimum estimate for tuberculosis proportion due to transmission was 20.1% with IS6110-RFLP and was 18.8% with MIRU and ETR. In conclusion, tuberculosis sanitation status in northwest of Iran due to minimum estimate of tuberculosis transmission was satisfactory, and the reactivation of tuberculosis was responsible for more than 80% of new tuberculosis. According to the results and drawbacks of IS6110-RFLP method we strongly recommend MIRU-VNTRplus ETR-VNTR as an easy, reliable, reproducible and highly discriminatory power method.