Genetic diversity of the<i>Mycobacterium tuberculosis</i>Beijing family in East Asia revealed through refined population structure analysis

The Beijing/W family is the endemic lineage of Mycobacterium tuberculosis in East Asia: it has disseminated worldwide. To elucidate its genetic diversity in Japan, phylogenetic reconstruction was performed using 403 M. tuberculosis Beijing family clinical isolates. Variable number of tandem repeats analysis revealed the strains from Japan to be dispersed mainly among five subgroups in a phylogenetic tree. Interestingly, the genotypes of the strains from China and Mongolia were restricted mainly to a single branch; they exhibited high clonality. IS6110 insertion in the NTF region was also analyzed. The majority (78.6%) of Japanese isolates belonged to the ancient sublineage. The modern Beijing strains were observed to correspond to the branch containing the foreign strains, although the ancient Beijing strains were dispersed among the tree's other branches. Our results reflect the singular genetic diversity and the epidemiological pattern of Beijing M. tuberculosis in Japan.