Analysis on genotyping of 159 strains of Mycobacterium tuberculosis isolated clinically in some areas of China with MLVA-19-Loci

Objective To investigate the polymorphic genetic characteristics of Mycobacterium tuberculosis(M.tuberculosis) strains isolated in China based on variable number of tandem repeats(VNTRs).Methods Nineteen tandem repeat loci were used for typing 159 randomly selected strains of M.tuberculosis isolated in some areas in China.The loci were analyzed by PCR and agarose gel electrophoresis respectively.The polymorphic genetic characteristics of DNA fingerprinting of these strains were detected with the BioNumerics 5.0 software.The results of genotyping were compared with the Intel-database of MLVA(http://minisatellites.u-psud.fr).Results 159 strains of M.tuberculosis were divided into 4 main clusters,the majority belonged to Beijing family cluster(73.8%),followed by H37Rv-like strains,BCG-like strains,and a no-matched cluster compared with the Inteldatabase.The tandem repeats characteristics of no-matched strains was that the repeat number of ETRD 3,MIRU10,MIRU27,MIRU39,MIRU40,and Mtub21 was 2,2,2,2,1 respectively,witch had significant difference with the strains of other cluster and might be a peculiar strain in China.A BCG like cluster was found too.Conclusion Obvious genetic polymorphism for the strains of M.tuberculosis isolated in China was observed in this study,The major strains belonged to Beijing family.There might be peculiar strains in the strains of M.tuberculosis isolated in China.The detection of BCG-like strains indicated that the BCG vaccine related cases might be a public health problem which should be pay attention to.