Exploring allosteric efflux pump inhibitors and the role of bacterial membrane potential in modulating drug resistance.

Multi-drug resistance (MDR) bacteria pose a significant global health challenge, primarily driven by the activity of multi-drug efflux pumps and their intimate coupling to bacterial membrane bioenergetics. Among these systems, proton-motive force (PMF) dependent Resistance, Nodulation-Division (RND) efflux pumps, such as AcrAB-TolC, play a central role in both intrinsic and acquired antibiotic resistance by expelling structurally diverse antimicrobial agents. Recent evidence indicates that efflux pumps are not merely drug extrusion devices but also key regulators of bacterial physiology, influencing membrane potential, redox balance, metabolic state, stress adaptation, and growth-phase transitions. Structural and mechanistic advances have uncovered conserved allosteric sites within RND pumps that are distinct from substrate-binding pockets, enabling the development of allosteric efflux pump inhibitors (EPIs) that disrupt conformational cycling and proton relay without competing with antibiotics. Pyridylpiperazine-based inhibitors, including BDM-series compounds, have demonstrated potent efflux inhibition, antibiotic potentiation, and