Chelerythrine potentiates meropenem activity against NDM-producing carbapenem-resistant Enterobacteriaceae

NDM-driven carbapenem-resistant Enterobacteriaceae (CRE) are spreading globally, posing a serious One Health threat that extends to veterinary medicine through transmission among food-producing animals, companion animals, and the farm-to-food continuum. Antibiotic adjuvants that restore or potentiate the activity of existing antibiotics represent a promising strategy to address this challenge.

In this study, we evaluated the ability of the natural benzophenanthridine alkaloid chelerythrine to potentiate meropenem activity against NDM-producing Enterobacteriaceae. Antibacterial synergy was assessed using checkerboard assays, resistance development assays, Galleria mellonella infection models, and a murine thigh infection model. The underlying mechanism was investigated through NDM enzymatic activity assays, Zn²⁺ competition experiments, molecular docking, molecular dynamics simulations, and bacterial physiological assays measuring proton motive force, ATP production, and reactive oxygen species (ROS) generation.

Chelerythrine strongly potentiated meropenem activity against blaNDM-1-, blaNDM-5-, and blaNDM-9-positive Enterobacteriaceae, with FICI values ranging from 0.18 to 0.31. Chelerythrine markedly delayed the emergence of meropenem resistance. Combination therapy increased survival to 75% in infected Galleria mellonella larvae and significantly reduced bacterial burden in the murine thigh infection model. Mechanistically, chelerythrine inhibited NDM enzymatic activity by occupying the catalytic pocket and interacting with residues surrounding the dinuclear Zn²⁺ center. In addition, chelerythrine caused extensive bacterial cellular damage by destabilizing the proton motive force, reducing ATP levels, and promoting ROS accumulation.

These findings demonstrate that chelerythrine restores meropenem efficacy against NDM-producing Enterobacteriaceae through a dual mechanism involving suppression of metallo-β-lactamase activity and induction of metabolic disruption. Chelerythrine therefore represents a promising meropenem adjuvant for combating NDM-mediated carbapenem resistance.