Evolutionary Convergence on a Dihydrofolate Reductase Mutation Drives Trimethoprim–Sulfamethoxazole Resistance in Burkholderia thailandensis
Abstract
Trimethoprim–sulfamethoxazole (SXT) remains central to melioidosis eradication therapy, yet the genetic basis of resistance evolution in Burkholderia pseudomallei is not fully defined. Using Burkholderia thailandensis as a biosafe surrogate, we subjected populations to stepwise in vitro evolution under increasing SXT concentrations. Whole-genome sequencing revealed rapid population diversification followed by selective sweeps leading to fixation of fitter resistant variants. Early adaptation involved mutations in regulators of RND efflux systems and folate-associated genes, consistent with multifactorial resistance. Despite this heterogeneity, all evolutionary trajectories converged on a single nonsynonymous substitution, I99L, in dihydrofolate reductase (DHFR/FolA), which rose to fixation at high SXT concentrations. This substitution mirrors changes reported in SXT-resistant B. pseudomallei isolates from chronic infections. Allelic reconstruction demonstrated that Bt-DHFR(I99L) is sufficient to confer a 4- to 16-fold increase in trimethoprim MIC. Biochemical and structural analyses showed preserved catalytic activity but reduced trimethoprim binding, consistent with an allosteric resistance mechanism. Together, these findings establish DHFR as a dominant evolutionary target under SXT pressure and support B. thailandensis as a robust model for dissecting resistance evolution in B. pseudomallei.
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BibTeX
@article{guillier2026evolutionary,
title = {{Evolutionary Convergence on a Dihydrofolate Reductase Mutation Drives Trimethoprim–Sulfamethoxazole Resistance in Burkholderia thailandensis}},
author = {Sophie Guillier and Christine Lazennec-Schurdevin and Lou Mondange and Véronique Sarilar and Mélissa Marchandeau and Chloé Lemoigne and Ombeline Lamer and Mathilde Lescat and Emmanuelle Schmitt and Yves Mechulam and Julian Garrec and Fabrice Biot},
journal = {ACS Infectious Diseases},
year = {2026},
month = aug,
doi = {10.1021/acsinfecdis.5c01132},
url = {https://polytechnique.hal.science/hal-05768761v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Evolutionary Convergence on a Dihydrofolate Reductase Mutation Drives Trimethoprim–Sulfamethoxazole Resistance in Burkholderia thailandensis
AU - Sophie Guillier
AU - Christine Lazennec-Schurdevin
AU - Lou Mondange
AU - Véronique Sarilar
AU - Mélissa Marchandeau
AU - Chloé Lemoigne
AU - Ombeline Lamer
AU - Mathilde Lescat
AU - Emmanuelle Schmitt
AU - Yves Mechulam
AU - Julian Garrec
AU - Fabrice Biot
PY - 2026
DA - 2026/08/05
JO - ACS Infectious Diseases
DO - 10.1021/acsinfecdis.5c01132
UR - https://polytechnique.hal.science/hal-05768761v1
AB - Trimethoprim–sulfamethoxazole (SXT) remains central to melioidosis eradication therapy, yet the genetic basis of resistance evolution in Burkholderia pseudomallei is not fully defined. Using Burkholderia thailandensis as a biosafe surrogate, we subjected populations to stepwise in vitro evolution under increasing SXT concentrations. Whole-genome sequencing revealed rapid population diversification followed by selective sweeps leading to fixation of fitter resistant variants. Early adaptation involved mutations in regulators of RND efflux systems and folate-associated genes, consistent with multifactorial resistance. Despite this heterogeneity, all evolutionary trajectories converged on a single nonsynonymous substitution, I99L, in dihydrofolate reductase (DHFR/FolA), which rose to fixation at high SXT concentrations. This substitution mirrors changes reported in SXT-resistant B. pseudomallei isolates from chronic infections. Allelic reconstruction demonstrated that Bt-DHFR(I99L) is sufficient to confer a 4- to 16-fold increase in trimethoprim MIC. Biochemical and structural analyses showed preserved catalytic activity but reduced trimethoprim binding, consistent with an allosteric resistance mechanism. Together, these findings establish DHFR as a dominant evolutionary target under SXT pressure and support B. thailandensis as a robust model for dissecting resistance evolution in B. pseudomallei.
SN - 2373-8227
ER -