Bayesian population structure analysis reveals presence of phylogeographically specific sublineages within previously ill-defined T group of Mycobacterium tuberculosis

PLoS One. 2017 Feb 6;12(2):e0171584. doi: 10.1371/journal.pone.0171584. eCollection 2017.

Abstract

Mycobacterium tuberculosis genetic structure, and evolutionary history have been studied for years by several genotyping approaches, but delineation of a few sublineages remains controversial and needs better characterization. This is particularly the case of T group within lineage 4 (L4) which was first described using spoligotyping to pool together a number of strains with ill-defined signatures. Although T strains were not traditionally considered as a real phylogenetic group, they did contain a few phylogenetically meaningful sublineages as shown using SNPs. We therefore decided to investigate if this observation could be corroborated using other robust genetic markers. We consequently made a first assessment of genetic structure using 24-loci MIRU-VNTRs data extracted from the SITVIT2 database (n = 607 clinical isolates collected in Russia, Albania, Turkey, Iraq, Brazil and China). Combining Minimum Spanning Trees and Bayesian population structure analyses (using STRUCTURE and TESS softwares), we distinctly identified eight tentative phylogenetic groups (T1-T8) with a remarkable correlation with geographical origin. We further compared the present structure observed with other L4 sublineages (n = 416 clinical isolates belonging to LAM, Haarlem, X, S sublineages), and showed that 5 out of 8 T groups seemed phylogeographically well-defined as opposed to the remaining 3 groups that partially mixed with other L4 isolates. These results provide with novel evidence about phylogeographically specificity of a proportion of ill-defined T group of M. tuberculosis. The genetic structure observed will now be further validated on an enlarged worldwide dataset using Whole Genome Sequencing (WGS).

MeSH terms

  • Alleles
  • Bayes Theorem*
  • Evolution, Molecular
  • Gene Dosage
  • Genotype
  • Minisatellite Repeats
  • Multilocus Sequence Typing
  • Mycobacterium tuberculosis / classification*
  • Mycobacterium tuberculosis / genetics*
  • Phylogeny*
  • Phylogeography*

Grants and funding

This work was supported by the European Regional Development Fund and European Social Fund (ERDF-ESF) under the scheme “Programme Opérationnel FEDER-FSE Guadeloupe Conseil Régional 2014–2020” (Grant number pending). Yann Reynaud was awarded a Calmette and Yersin postdoctoral fellowship by the Institut Pasteur International Network. Chao Zheng was financially supported by China Scholarship Council (CSC, File NO.201506240129) under a co-training program for the fulfillment of his PhD research program between College of Life Sciences, Sichuan University, Chengdu, China, and Tuberculosis and Mycobacteria Unit, Institut Pasteur de la Guadeloupe.