A trimethoprim derivative impedes antibiotic resistance evolution

Abstract

The antibiotic trimethoprim (TMP) is used to treat a variety of Escherichia coli infections, but its efficacy is limited by the rapid emergence of TMP-resistant bacteria. Previous laboratory evolution experiments have identified resistance-conferring mutations in the gene encoding the TMP target, bacterial dihydrofolate reductase (DHFR), in particular mutation L28R. Here, we show that 4’-desmethyltrimethoprim (4’-DTMP) inhibits both DHFR and its L28R variant, and selects against the emergence of TMP-resistant bacteria that carry the L28R mutation in laboratory experiments. Furthermore, antibiotic-sensitive E. coli populations acquire antibiotic resistance at a substantially slower rate when grown in the presence of 4’-DTMP than in the presence of TMP. We find that 4’-DTMP impedes evolution of resistance by selecting against resistant genotypes with the L28R mutation and diverting genetic trajectories to other resistance-conferring DHFR mutations with catalytic deficiencies. Our results demonstrate how a detailed characterization of resistance-conferring mutations in a target enzyme can help identify potential drugs against antibiotic-resistant bacteria, which may ultimately increase long-term efficacy of antimicrobial therapies by modulating evolutionary trajectories that lead to resistance.

Development of antibacterial compounds that constrain evolutionary pathways to resistance

“…The L28R mutation also shows improved compactness, inferred from its reduced bis-ANS binding ( Rodrigues et al, 2016 ). Thus, among the evolved mutant E. coli strains, L28R is one of the most frequently encountered resistance mutations in folA gene which render traditional anti-folate drugs like TMP clinically ineffective ( Manna et al, 2021 ; Rodrigues et al, 2016 ; Toprak et al, 2012 ). Effectively L28R serves as a stability ‘reservoir’ providing a gateway to multiple evolutionary trajectories leading to resistance.…”

Antivitamins: A Silver Lining in the Era of Antimicrobial Resistance

“…Moreover, it confers mutations at a markedly slower rate as compared to TMP and hampers the development of resistant mutations. 42…”

Structure-guided functional studies of plasmid-encoded dihydrofolate reductases reveal a common mechanism of trimethoprim resistance in Gram-negative pathogens

“…Through phylogenic and sequence analysis, we identified two critical residue variations as a common structural element in trimethoprim-resistant DHFR, D27E and L28Q. The potential role of mutation to the acidic residue in TMP resistance has been considered in earlier work 22 – 25 Complementing biochemical and biophysical analysis defined how these substitutions mediate trimethoprim-resistance in DfrA1 and DfrA5 through effects on enzyme catalysis and ligand-cofactor cooperativity. These conclusions were supported by high-resolution structural data, paving the way for a design of next-generation broad-spectrum antifolates.…”