Antibiotics are losing efficacy due to the rapid evolution and spread of resistance. Treatments targeting bacterial virulence factors have been considered as alternatives because they target virulence instead of pathogen viability, and should therefore exert weaker selection for resistance than conventional antibiotics. However, antivirulence treatments rarely clear infections, which compromises their clinical applications. Here, we explore the potential of combining antivirulence drugs with antibiotics against the opportunistic human pathogen Pseudomonas aeruginosa. We combined two antivirulence compounds (gallium, a siderophore quencher, and furanone C-30, a quorum sensing [QS] inhibitor) together with four clinically relevant antibiotics (ciprofloxacin, colistin, meropenem, tobramycin) in 9×9 drug concentration matrices. We found that drug-interaction patterns were concentration dependent, with promising levels of synergies occurring at intermediate drug concentrations for certain drug pairs. We then tested whether antivirulence compounds are potent adjuvants, especially when treating antibiotic resistant (AtbR) clones. We found that the addition of antivirulence compounds to antibiotics could restore growth inhibition for most AtbR clones, and even abrogate or reverse selection for resistance in five drug combination cases. Molecular analyses suggest that selection against resistant clones occurs when resistance mechanisms involve restoration of protein synthesis, but not when efflux pumps are up-regulated. Altogether, our work provides a first systematic analysis of antivirulence-antibiotic combinatorial treatments and suggests that such combinations have the potential to be both effective in treating infections and in limiting the spread of antibiotic resistance.

由于耐药性的快速进化和传播，抗生素正在失去功效。针对细菌毒力因子的治疗已被认为是替代方案，因为它们针对的是毒力而不是病原体活力，因此对耐药性的选择应比传统抗生素弱。然而，抗毒治疗很少能清除感染，这损害了其临床应用。在这里，我们探索将抗毒药物与抗生素结合起来对抗机会性人类病原体铜绿假单胞菌的潜力。我们将两种抗毒化合物（镓，一种铁载体猝灭剂和呋喃酮 C-30，一种群体感应 [QS] 抑制剂）与四种临床相关抗生素（环丙沙星、粘菌素、美罗培南、妥布霉素）组合在 9×9 药物浓度矩阵中。我们发现药物相互作用模式是浓度依赖性的，对于某些药物对来说，在中间药物浓度下会出现有希望的协同作用水平。然后我们测试了抗毒化合物是否是有效的佐剂，特别是在治疗抗生素耐药性（AtbR）克隆时。我们发现，在抗生素中添加抗毒化合物可以恢复大多数 AtbR 克隆的生长抑制，甚至在 5 种药物组合案例中取消或逆转耐药性选择。分子分析表明，当抗性机制涉及蛋白质合成恢复时，就会发生针对抗性克隆的选择，但当外排泵上调时则不会。总而言之，我们的工作首次对抗毒力-抗生素组合治疗进行了系统分析，并表明这种组合有可能既能有效治疗感染，又能有效限制抗生素耐药性的传播。