泛耐药肺炎克雷伯菌抗噬菌体突变后对抗生素耐药性减弱的机制研究

超级细菌感染是器官移植受者死亡的主要原因之一。噬菌体作为细菌的天敌，在防治超级细菌感染上具有重要潜力。我们在噬菌体治疗临床试验中发现，当患者基础免疫力低下时，泛耐药肺炎克雷伯菌依然可以对噬菌体产生耐受现象，导致感染复发。我们的研究发现，已被细菌耐药的复方新诺明（SMZ-TMP）却能协同抑制噬菌体耐受菌的出现，从而达到联合治愈超级细菌感染的目的。耐受噬菌体的菌株对SMZ-TMP的敏感性由原来的320μg/ml降低到160μg/ml，由于SMZ-TMP主要由肾脏排除，尿液中的浓度可超过160μg/ml，足以清除清除噬菌体耐受菌。本课题拟用全基因组测序、基因敲除、回补及生化实验的方法，阐明肺炎克雷伯菌对噬菌体的耐受机制，揭示耐受菌对SMZ-TMP的耐药性下降与细菌膜通透性改变的关系。本研究有望揭示噬菌体抗生素联用的协同机制，为今后指导噬菌体治疗试验提供理论依据。

Superbug infection is one of the leading causes of death in organ-transplant recipients. Bacteriophage, known as bacterial virus, has important potential in the prevention and treatment of superbug infections. In our clinical practices of phage therapy, we found that multidrug-resistant bacteria commonly become resistant to phages and lead to recurrent infection in immunocompromised patients. In our previous study, we found that, SMZ-TMP, which the bacteria had already resisted to, synergistically inhibited the emergence of phage-resistant bacteria, thereby curing a pan-resistant Klebsiella pneumoniae in urinary tract infection. In vitro experiments demonstrated that the minimum inhibitory concentration (MIC) of phage-tolerant strains against SMZ-TMP was reduced from 320 μg/ml to 160 μg/ml. Since SMZ-TMP is mainly excreted by the kidney, its concentration in urine is sufficient enough to kill phage-resistant mutants. Therefore, this project proposes to elucidate the mechanism of phage tolerance in K. pneumoniae using whole-genome sequencing, gene knockout, complementation assay and biochemical experiments, and to further reveal the relationship between the decreased SMZ-TMP resistance and the increased membrane permeability in phage-resistant mutants. This porject is likely to reveal the synergistic mechanism of phage antibiotic combination and provide a theoretical basis for phage therapy practices.