Evolutionary Stability of Genetically Induced Trimethoprim Hypersensitivity in Escherichia coli

Abstract

Antibiotic resistance has compromised the ability to treat resistant infections and is a significant public health concern of the 21st century. These antibiotic resistant bacteria may possess natural intrinsic drug resistance such as due to a permeability barrier or acquire resistance by gaining mutations or new genetic material coding for antibiotic degrading enzymes. Several strategies such as bacteriophage therapy, antibiotic combination therapy and adjuvant therapy are currently being explored to reverse resistance. While the discovery of compounds that can reverse resistance is important, the identification of molecular targets that can modulate resistance is also equally crucial. Further, the evolutionary stabilities of the susceptibilities conferred by these targets is vital to ensure their introduction as therapeutics. In this study, we identified three potential targets of intrinsic resistance, rfaG, lpxM and acrB, that when deleted could modulate antibiotic susceptibilities and reverse trimethoprim resistance of Escherichia coli. At high trimethoprim concentrations, all 3 gene knockouts were jeopardised in their ability to recover from drug sensitivity. At low antibiotic concentrations however, they could evolve different extents of resistance by fixing different mutations that enabled them to adapt to trimethoprim. Significantly, the chemical inhibition of the AcrB target led to resistance evolution surpassing that of the evolved knockout, highlighting that they may overcome resistance through alternate mechanisms, and emphasising the need for monitoring and administration in antibiotic therapy.