title: Convergent evolutionary analysis identifies significant mutations in drug resistance targets of Mycobacterium tuberculosis.
abstract: Mycobacterium tuberculosis adapts to the environment by selecting for advantageous single-nucleotide polymorphisms (SNPs). We studied whether advantageous SNPs could be distinguished from neutral mutations within genes associated with drug resistance. A total of 1,003 clinical isolates of M. tuberculosis were related phylogenetically and tested for the distribution of SNPs in putative drug resistance genes. Drug resistance-associated versus non-drug-resistance-associated SNPs in putative drug resistance genes were compared for associations with single versus multiple-branch outcomes using the chi-square and Fisher exact tests. All 286 (100%) isolates containing isoniazid (INH) resistance-associated SNPs had multibranch distributions, suggestive of multiple ancestry and convergent evolution. In contrast, all 327 (100%) isolates containing non-drug-resistance-associated SNPs were monophyletic and thus showed no evidence of convergent evolution (P < 0.001). Convergence testing was then applied to SNPs at position 481 of the iniA (Rv0342) gene and position 306 of the embB gene, both potential drug resistance targets for INH and/or ethambutol. Mutant embB306 alleles showed multibranch distributions, suggestive of convergent evolution; however, all 44 iniA(H481Q) mutations were monophyletic. In conclusion, this study validates convergence analysis as a tool for identifying mutations that cause INH resistance and explores mutations in other genes. Our results suggest that embB306 mutations are likely to confer drug resistance, while iniA(H481Q) mutations are not. This approach may be applied on a genome-wide scale to identify SNPs that impact antibiotic resistance and other types of biological fitness.
authors.affiliation: Department of Medicine, Division of Infectious Disease, Ruy V Lourenço Center for the Study of Emerging and Re-emerging Pathogens, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA.
authors.forename: Manzour Hernando
authors.initials: MH
authors.lastname: Hazbón
authors.forename: Alifiya S
authors.initials: AS
authors.lastname: Motiwala
authors.forename: Magali
authors.initials: M
authors.lastname: Cavatore
authors.forename: Michael
authors.initials: M
authors.lastname: Brimacombe
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Whittam
authors.forename: David
authors.initials: D
authors.lastname: Alland
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004977:Ethambutol / Q000494:pharmacology; D019143:Evolution, Molecular; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D004977:Ethambutol; D007538:Isoniazid