title: Evolution of high-level ethambutol-resistant tuberculosis through interacting mutations in decaprenylphosphoryl-β-D-arabinose biosynthetic and utilization pathway genes.
abstract: To study the evolution of drug resistance, we genetically and biochemically characterized Mycobacterium tuberculosis strains selected in vitro for ethambutol resistance. Mutations in decaprenylphosphoryl-β-D-arabinose (DPA) biosynthetic and utilization pathway genes Rv3806c, Rv3792, embB and embC accumulated to produce a wide range of ethambutol minimal inhibitory concentrations (MICs) that depended on mutation type and number. Rv3806c mutations increased DPA synthesis, causing MICs to double from 2 to 4 μg/ml in a wild-type background and to increase from 16 to 32 μg/ml in an embB codon 306 mutant background. Synonymous mutations in Rv3792 increased the expression of downstream embC, an ethambutol target, resulting in MICs of 8 μg/ml. Multistep selection was required for high-level resistance. Mutations in embC or very high embC expression were observed at the highest resistance level. In clinical isolates, Rv3806c mutations were associated with high-level resistance and had multiplicative effects with embB mutations on MICs. Ethambutol resistance is acquired through the acquisition of mutations that interact in complex ways to produce a range of MICs, from those falling below breakpoint values to ones representing high-level resistance.
authors.affiliation: 1] Division of Infectious Disease, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA. [2] Center for Emerging and Re-emerging Pathogens, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA. [3] Department of Medicine, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA.
authors.forename: Hassan
authors.initials: H
authors.lastname: Safi
authors.forename: Subramanya
authors.initials: S
authors.lastname: Lingaraju
authors.forename: Anita
authors.initials: A
authors.lastname: Amin
authors.forename: Soyeon
authors.initials: S
authors.lastname: Kim
authors.forename: Marcus
authors.initials: M
authors.lastname: Jones
authors.forename: Michael
authors.initials: M
authors.lastname: Holmes
authors.forename: Michael
authors.initials: M
authors.lastname: McNeil
authors.forename: Scott N
authors.initials: SN
authors.lastname: Peterson
authors.forename: Delphi
authors.initials: D
authors.lastname: Chatterjee
authors.forename: Robert
authors.initials: R
authors.lastname: Fleischmann
authors.forename: David
authors.initials: D
authors.lastname: Alland
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001089:Arabinose / Q000096:biosynthesis* / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004977:Ethambutol / Q000494:pharmacology / Q000627:therapeutic use*; D019143:Evolution, Molecular; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects*
chemical_list: D000995:Antitubercular Agents; D004977:Ethambutol; D001089:Arabinose