[Preliminary study on genotyping of Mycobacterium tuberculosis strains isolated in Tibet with multiple locus variable numbers of tandem repeats].

OBJECTIVE: To investigate the application of the multiple locus variable numbers of tandem repeats (MLVA) in genotype Mycobacterium tuberculosis strains isolated from Tibet, and to understand the characteristics of genotype and distribution. METHODS: 217 M. tuberculosis strains were collected from six regions of Tibet. Twenty tandem repeats loci in the total genome of M. tuberculosis (MTB) were analyzed by PCR and agarose gel electrophoresis method. The characteristics on polymorphism of DNA fingerprinting of 217 MTB strains were analyzed with BioNumerics 3.0 software. RESULTS: 217 M. tuberculosis strains detected with 20 MLVA loci were classified to 19 genotypes with 87.6% of the stains belonging to Beijing genotype and the other 18 genotypes were scattered,accounted for 1.38% and 0.92% strains, respectively. Beijing genotype was not significantly associated with the resistance to all of the four drugs and BCG vaccination. CONCLUSION: It is concluded that the strains of MTB isolated in Tibet present definite polymorphism and most of the epidemic strains belonged to Beijing family genotype and MTB genotyping. The Beijing genotype was not recognized as the one transferred from some of the drug resistance strains or from BCG vaccination. Being a fast and simple technique, MLVA method, seemed a better molecular typing method and could be used for genotyping in M. tuberculosis and monitoring pathogen.