Comparison of Mycobacterium tuberculosis Beijing genotype with other Mycobacterium tuberculosis strains Using MIRU-VNTR method

Abstract

Background: Recently it is shown that Mycobacterium tuberculosis Beijing genotype are associated with drug resistance. Thus a simple and rapid method is required for identification and differentiation of Beijing family isolates. Therefore the aim of this study is to evaluate discriminatory power of different loci in both 12 MIRU-VNTR and 15 MIRU-VNTR Methods for Beijing genotype. Methods: In total 105 Mycobacterium tuberculosis strains were identified by spoligotyping, then genomic analysis was carried out by using 12 and 15 MIRU-VNTR methods. Allelic diversity for each locus was calculated using Hunter Gaston Discriminatory Index (HGI). Results: With spoligotyping 20 out of 105 isolates (19.05%) belonged to the Beijing family. Investigating all strains with 12 and 15 MIRU-VNTR showed that 11 loci were highly discriminative (HGI≥0.6) and QUB26 had the highest discriminatory power (HGI=0.84). Number of repeats in QUB11b was specific for Beijing genotype, and only MIRU16 was highly discriminator for this genotype. QUB26, Mtub21, MIRU39, MIRU27, MIRU23 and MIRU26 were moderately discriminator (0.4≤HGI<0.6) and other loci were poorly discriminator for Beijing strains (HGI<0.4). Conclusion: 12 and 15 locus MIRU-VNTR are simple and rapid methods and suitable for differentiation of Beijing genotype from other MTB strains, however these two methods are not suitable for discriminating Beijing family among themselves. In overall discriminatory power of 15 locus MIRU-VNTR method was higher than 12 locus MIRU-VNTR.

Keywords

• MIRU-VNTR
• mycobacterium tuberculosis
• Beijing genotype
• tuberculosis