A-329

As antibiotic resistance increases and new drug development lags, the effectiveness of single antibiotics has drastically diminished for clinical infection treatment. The resistance crisis is exacerbated by the swift development and dissemination of Gram-negative bacteria that are extensively drug-resistant (XDR), particularly strains resistant to carbapenems in clinical settings. In this scenario, antibiotic adjuvants play a crucial role in revitalizing existing treatments to combat carbapenem-resistant bacterial infections. In this study, we synthesized ten small molecular antimicrobial peptide mimics and identified antimicrobial peptide mimic 329 (A329), which exhibited a synergistic effect with minocycline (FICI = 0.023), enhancing its efficacy by 4- to 128-fold, and significantly enhanced the antibacterial efficacy of minocycline against carbapenem-resistant Klebsiella pneumoniae (CRKP, 0.015 ≤ FICI ≤0.141), prevented the emergence of minocycline resistance, improved the survival rate of mice, and decreased bacterial load in tissues at 8 + 8 mg/kg. Mechanistic studies revealed that A329 increases bacterial membrane permeability and disrupts the proton-motive force. Additionally, A329 combined with minocycline boosts intracellular minocycline accumulation, induces intracellular production of reactive oxygen species (ROS), and ultimately triggers bacterial death. These findings advised that A329 in combination with minocycline is a potential combination therapy against XDR-associated infections.