Glutamine Potentiates Cefoperazone-Sulbactam Activity against <i>Acinetobacter baumannii</i> by Increasing Drug Uptake and ROS

The combination of an antibiotic with a metabolic reprogramming agent is anticipated to emerge as a promising therapeutic strategy against antibiotic-resistant bacteria, although this hypothesis requires validation through preclinical pharmacodynamic studies. This study evaluated the preclinical pharmacodynamic profile of cefoperazone-sulbactam (SCF) combined with glutamine against 237 <i>Acinetobacter baumannii</i> clinical isolates, including 26 antibiotic-sensitive (S-AB), 8 multidrug-resistant (MDR-AB), and 203 carbapenem-resistant strains (CR-AB). The combination demonstrated synergistic efficacy in 224 cases (94.51%), equivalence in 10 (4.22%), and no interaction in 3 (1.27%) compared with SCF monotherapy. Time-kill assays, bacterial load quantification, and murine infection models consistently validated these findings, with therapeutic effects remaining stable despite variations in calcium concentrations and pH gradients. Glutamine slows the development of SCF resistance, prolongs the postantibiotic effect, and reduces mutation frequency. Mechanistically, glutamine reprograms bacterial metabolism from an antibiotic-resistant state to an antibiotic-sensitive state, thereby enhancing reactive oxygen species (ROS) production, which combines with increased drug uptake to potentiate SCF killing. This accelerated drug influx surpasses the clearance capacity mediated by efflux pumps and enzymatic degradation, resulting in increased bacterial eradication through synergy with ROS. These findings suggest that the synergistic combination holds the potential for developing therapeutic candidates against MDR-AB and CR-AB.