Table_3_The Capsule Depolymerase Dpo48 Rescues Galleria mellonella and Mice From Acinetobacter baumannii Systemic Infections.DOC

The emergence of multidrug- and extensively drug-resistant Acinetobacter baumannii has made it difficult to treat and control infections caused by this bacterium. Thus, alternatives to conventional antibiotics for management of severe A. baumannii infections is urgently needed. In our previous study, we found that a capsule depolymerase Dpo48 could strip bacterial capsules, and the non-capsuled A. baumannii were significantly decreased in the presence of serum complement in vitro. Here, we further explored its potential as a therapeutic agent for controlling systemic infections caused by extensively drug-resistant A. baumannii. Prior to mammalian studies, the anti-virulence efficacy of Dpo48 was first tested in a Galleria mellonella infection model. Survival rate of Dpo48-pretreated bacteria or Dpo48 treatment group was significantly increased compared to the infective G. mellonella without treatment. Furthermore, the safety and therapeutic efficacy of Dpo48 to mice were evaluated. The mice treated with Dpo48 displayed normal serum levels of TBIL, AST, ALT, ALP, Cr, BUN and LDH, while no significant histopathology changes were observed in tissues of liver, spleen, lung, and kidney. Treatment with Dpo48 could rescue normal and immunocompromised mice from lethal peritoneal sepsis, with the bacterial counts in blood, liver, spleen, lung, and kidney significantly reduced by 1.4–3.3 log colony-forming units at 4 h posttreatment. Besides, the hemolysis and cytotoxicity assays showed that Dpo48 was non-homolytic to human red blood cells and non-toxic to human lung, liver and kidney cell lines. Overall, the present study demonstrated the promising potential of capsule depolymerases as therapeutic agents to prevent antibiotic-resistant A. baumannii infections.

多药耐药和广泛耐药鲍曼不动杆菌的出现，使得该细菌引起的感染治疗与控制变得尤为困难。因此，对于严重鲍曼不动杆菌感染的管理，迫切需要寻求传统抗生素之外的替代方案。在我们之前的研究中，我们发现一种囊泡解聚酶Dpo48能够去除细菌囊泡，体外实验中，去囊泡的鲍曼不动杆菌在血清补体存在的情况下显著减少。在本研究中，我们进一步探讨了Dpo48作为治疗剂控制广泛耐药鲍曼不动杆菌引起的全身性感染的可能性。在进行哺乳动物研究之前，Dpo48的抗致病力首先在一个甘蓝夜蛾感染模型中进行测试。与未经治疗的感染甘蓝夜蛾相比，预先用Dpo48处理的细菌或Dpo48处理组的存活率显著提高。此外，对小鼠进行Dpo48的治疗效果和安全性的评估显示，接受Dpo48治疗的小鼠血清中的TBIL、AST、ALT、ALP、Cr、BUN和LDH水平均正常，而在肝脏、脾脏、肺和肾脏的组织中未观察到显著的病理学变化。Dpo48治疗能够拯救正常和免疫缺陷小鼠免受致命性腹膜炎的影响，治疗4小时后，血液、肝脏、脾脏、肺和肾脏中的细菌计数显著减少，减少幅度为1.4至3.3个对数级的菌落形成单位。此外，溶血和细胞毒性实验表明，Dpo48对人类红细胞无溶血作用，对人类肺、肝和肾脏细胞系无毒。总体而言，本研究展示了囊泡解聚酶作为治疗剂预防抗生素耐药鲍曼不动杆菌感染的巨大潜力。