Objective: To introduce a new genotyping method, mycobacterial interspersed repetitive units (MIRU) typing, for Mycobacterium tuberculosis and to evaluate its feasibility.
Methods: Mycobacterium tuberculosis strains stored at Shanghai Municipal Center for Disease Control and Prevention during 2000 to 2002, were randomly selected by simple digital table and genotyped by MIRU and Spoligotyping.
Results: By Spoligotyping method, 91 strains were typed to 20 genotypes, of which 89% (81/91) strains belonged to Beijing genotype, while by MIRU method, these strains were divided into 46 genotypes. The MIRU typing showed high discriminatory power, especially for the Beijing genotype strains. The 81 Beijing genotype strains could be subdivided into 39 different MIRU genotypes. In this sample collection, 12 MIRU loci showed different discriminative according to their allelic diversity. Locus 26 showed highly discriminative, while locus 16, 31, and 40 showed moderately discriminative.
Conclusions: MIRU genotyping is a simple and fast method. Its numerical result facilitates the comparison among strains of Mycobacterium tuberculosis from different labs.