Origin, phylogeny, and spread of Mycobacterium tuberculosis Beijing lineage in the five provinces of northern China

Abstract

Using methodology of molecular genetics to explore the origin, phylogen, and gene flow of Mycobacterium tuberculosis (MTB) Beijing lineage in the five provinces from northern China, including Heilongjiang, Jilin, Liaoning, Neimenggu and Ningxia. 234 MTB Beijing lineage strains were genotyped by 24 Variable Number Tandem Repeat (VNTR), and the h (the allelic diversity) value of each VNTR locus was calculated. On individual level of phylogeny, it was constructed Neighbor-Joining (N-J) tree and minimum spanning tree (MST). Phylogenetic tree was built at the population level, and the most recent common ancestor (TMRCA) was estimated through Bayesian model. Molecular variance (AMOVA) was used to understand the gene flow among strains discovered from the five provinces. Allelic diversities of the 24 VNTR loci were low (h: 0.000 - 0.744). 234 strains of MTB Beijing lineage were dispersed in individual branch of the N-J tree, with 62.0% (145) of them grouped to the same "colonial complexes" in MST. At the population level, the evolution relationship of 234 strains appeared the closest to Beijing lineage, which was from MIRU-VNTRplus database, and the bootstrap was 100. The TMRCA was 5308 (95%CI: 4263 - 6470) years. Differences of pairwise Fst values acquired by AMOVA between Jilin and Heilongjiang, Liaoning, Neimenggu and Ningxia, were not statistically significant (P > 0.05). The genetic similarity of Beijing lineage MTB from the five provinces of northern China was high. The phylogeny branches had no characteristic dispersal in each province. It was speculated that these strains showed an evolution from a clone of MTB Beijing lineage (about 5000 years ago). The gene flow was taking place between neighboring zones.