OBJECTIVEVariable Number of Tandem Repeats (VNTRs) analysis was a recently developed method which could serve as a 'real-time' genotyping tool for Mycobacterium tuberculosis. One hundred and thirteen M. tuberculosis isolates from the patients with tuberculosis in Beijing were analysed using the reference method to study the characters of genetic diversity and genotype.

METHODSThirteen tandem repeat loci (ETR-A, ETR-C, ETR-D, MIRU10, MIRU16, MIRU27, MIRU31, MIRU40, Mtub21, Mtub30, Mtub38, Qublla, Qubllb) in the total genome of MTB were analyzed by PCR and agarose gel electrophoresis method. The characters of the polymorphism of DNA fingerprinting of one hundred and thirteen MTB strains were analyzed with Gel-Pro analyzer 3.1 software and BioNumerics 3.0 software. Results One hundred and thirteen MTB strains were characterized and classified in to four genotype families(type I , type II , type NV, type V ) based on thirteen tandem repeat loci. One hundred and four isolates(92.0%) belonged to type I , the other three genotypes scattered, five strains(4.4%) remaining with type II , while type IV and type V having the same quantity 1.8% (2/113). M. tuberculosis H37Rv belonged to a unattached genotype(type ll ). Conclusion There was obvious length polymorphism in the M. tuberculosis isolates which implied that type I was the epidemic strain clusters in M. tuberculosis in Beijing. VNTRs analysis seemed to be a simple, rapid, sensitive and valuable tool for epidemiological studies of M. tuberculosis complex organisms.