Synchronous Comparison of Mycobacterium tuberculosis Epidemiology Strains by “MIRU-VNTR” and “MIRU-VNTR and Spoligotyping” Technique

Molecular epidemiology analyses are frequently used in determining epidemiology of tuberculosis. Recently, Mycobacterial Interspersed Repetitive Unit Variable Number Tandem Repeat (MIRU-VNTR) and Spoligotyping has become an important method, as it allows high-through put, discriminatory and reproducible analysis of clinical isolate. The purpose of this study is to compare techniques of “MIRU-VNTR” versus “MIRU-VNTR and Spoligotyping” together for study of genetic pattern of Mycobacterium tuberculosis (M. tuberculosis) strains. Sixty M. tuberculosis (MTB) isolates were selected (30 susceptible, 30 multi-drug resistant) for this study. Thereafter, the “MIRU-VNTR and Spoligotyping” were performed to identify their genetic patterns. The frequency of unknown genetic pattern of MTB was compared using technique of “MIRU-VNTR” alone versus “MIRU-VNTR and Spoligotyping” together. The MIRU-VNTR allelic diversity at each of the loci was calculated by Hunter – Gaston Discriminatory Index (HGDI). Based on differentiation index of all strains 10, 16, 26, 31 and 40 loci were identified as the most distinctive (HGI ≥0.6) and 2, 4, 20 and 24 as the weakest distinctive locus (HGI ≤0.3). By using MIRU-VNTR technique 38% (n = 23) of isolates could not be typed, whereas by applying “MIRU-VNTR and Spoligotyping” together only 15% (n = 9) of isolates remained unknown (p = 0.004). For sensitive strains, the difference was significant (67% vs. 90%, p = 0.028), but only marginally significant for drug resistant strains (57% vs. 80%, p = 0.052). The discrimination power of 12-locus MIRU-VNTR and Spoligotyping was equal to that of MIRU-VNTR analysis. If appropriate loci are added to the standard MIRU analysis, MIRU-VNTR genotyping could be a valuable tool for strain typing and epidemiological research of M. tuberculosis. With this approach a more clear understanding about genetic pattern of MTB can be achieved.