With the stagnancy of antibiotics development, polymyxins have become the last defense for treatment of multidrug-resistant (MDR) Gram-negative bacteria, whereas the effect of polymyxin monotherapy is limited by resistance. The objective of this study was to evaluate the effects of polymyxin B (PMNB)-vorinostat (SAHA) combination therapy against Gram-negative pathogens in vitro and in vivo. The antibacterial activities of PMNB and SAHA were evaluated by susceptibility testing. The synergistic effect was assessed by checkerboard tests and time-killing kinetics experiments. Cellular morphology studies and reactive oxygen species (ROS) assay were conducted to explore potential mechanisms. Also, Galleria mellonella models were made to evaluate the antibacterial effects in vivo. PMNB-SAHA had the synergistic effect against all tested isolates, reducing >2 log₁₀ colony-forming units (CFU)/mL at 40 minutes, and showed more powerful antibacterial effects than PMNB alone in the 24-hour window. Cellular morphology study showed the change of membrane and disruption of integrity. ROS assay showed more oxidative stress in combination than PMNB or SAHA monotherapy. In animal models, PMNB-SAHA showed a higher survival rate than that of monotherapy. This study is the first to report the synergistic antibacterial effect of PMNB-SAHA therapy against MDR Gram-negative bacteria. Further clinical research is needed to confirm the results.

中文翻译：

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对抗多药耐药革兰氏阴性病原菌的多粘菌素-伏立诺他联合疗法的体外和体内作用。

随着抗生素的发展停滞，多粘菌素已成为治疗多药耐药（MDR）革兰氏阴性细菌的最后防御方法，而多粘菌素单一疗法的效果受到耐药性的限制。本研究的目的是评估多粘菌素B（PMNB）-vorinostat（SAHA）组合疗法的抗革兰氏阴性菌的影响在体外和体内。通过药敏试验评估了PMNB和SAHA的抗菌活性。协同作用通过棋盘测试和消灭动力学实验进行评估。进行了细胞形态学研究和活性氧（ROS）测定，以探索潜在的机制。另外，马隆广场建立模型评估体内抗菌效果。PMNB-SAHA对所有测试的分离物均具有协同作用，在40分钟时可降低> 2 log ₁₀菌落形成单位（CFU）/ mL，并且在24小时内比单独使用PMNB表现出更强大的抗菌作用。细胞形态学研究显示膜的变化和完整性的破坏。ROS分析显示，与PMNB或SAHA单药治疗相比，联合使用的氧化应激更大。在动物模型中，PMNB-SAHA的存活率高于单一疗法。这项研究是第一个报告PMNB-SAHA疗法对MDR革兰氏阴性菌的协同抗菌作用。需要进一步的临床研究以确认结果。