Study of genetic diversity of M.tuberculosis strains isolated by MIRU-VNTR technique in Masih Daneshvari Hospital, Tehran

Nowadays, MDR strains of mycobacterium tuberculosis are a serious problem in many countries which poses difficulties for TB control program. Since 1990s, spread of MDR TB cases in different parts of the world have been reported which is mainly because of incorrect use of TB drugs. One of the main causes of drug resistance occurring as a complication of human mistakes can be wrong classification and lack of monitoring of the patients during treatment and lack of supervision on the consumption of anti TB drugs. The purpose of this study was to investigate genetic diversity of M.tuberculosis strains isolated from patients by means of MIRU-VNTR technique. In this study 96 mycobacterium tuberculosis strains were isolated from the patients with pulmonary tuberculosis and drug sensitivity tests was performed by MIRU-VNTR technique. Genetic diversity of the strains based on MIRU-VNTR loci was estimated. Allelic difference of each loci was determined by means of statistical HGDI formula. Genetic pattern of sensitive strains showed that these strains belong to families of Dehli/CAS, Haarlem, LAM, H37RV and Caprae. Most drug resistant strains had genetic pattern of Haarlem and LAM families. Loci allelic differences between sensitive and resistant strains were not significant. Based on differentiation index of all strains, 10, 16, 26, 31 and 40 loci had the most allelic differences (HGI ≥ 0.6) and 2, 4, 20, 24 and 27 loci had the least differences (HGI ≤ 0.3). The results showed that most genetic diversity of sensitive and resistant strains belonged to Haarlem and Dhli/CAS families and MIRU-VNTR technique used in this study for determination of genetic diversity of mycobacterium strains is a rapid, accurate and cheap method which can be used easily in the populations with high frequency of TB.