靶向K47型肺炎克雷伯菌抗菌蛋白的鉴定及其特异性分子基础研究

肺炎克雷伯菌（简称“肺克”）是引起院内外感染的重要致病菌之一，其耐药性逐年增强，给临床治疗带来巨大挑战。噬菌体及其来源抗菌蛋白能够有效杀灭细菌，有望作为抗生素替代或补充的有效手段。然而，噬菌体及其抗菌蛋白的宿主特异性较强，且其特异性分子基础尚不清楚。此前，申请人从一株肺克噬菌体中鉴定出两种解聚酶类抗菌蛋白，具有较好的抗菌效果。进一步研究发现，这两种蛋白并不能杀灭所有K47型肺克。因此，本项目拟继续分离鉴定特异性靶向K47型肺克的解聚酶，建立解聚酶类抗菌蛋白库，为控制该型细菌感染提供抗生素以外的手段。在此基础上，利用解聚酶特异性将K47型肺克分成不同亚群，对不同亚群代表性菌株进行高通量测序与系统进化分析，建立解聚酶特异性亚群与分子进化亚群的对应关系，寻找决定解聚酶特异性的关键基因区域或关键基因，阐明解聚酶特异性作用K47型肺克的分子基础，为临床耐药肺克感染的个体化精准治疗提供新思路和新方法。

Klebsiella pneumoniae is an opportunistic pathogen causing community- and hospital-acquired infections. The emergence of drug-resistant K. pneumoniae has significantly increased the therapeutic challenges of managing the associated infections. Bacteriophage (phage) and its-derived depolymerases have recently been proposed as promising alternative or adjunctive treatment strategies to antibiotics against drug-resistant K. pneumoniae. Though phage and its-derived depolymerases are known to have excellent host specificity, knowledge of the governance mechanisms are rather limited. Previously, the applicant have identified two depolymerases from a K. pneumoniae phage, exhibiting potent antibacterial activity against capsular type K47 K. pneumoniae strains. However, our further studies indicated that these two depolymerases were not able to target all K47 K. pneumoniae strains. Therefore, the objective of the project is isolate and identify more phage-derived depolymerases targeting K47 K. pneumoniae and establish a comprehensive depolymerase library, facilitating the development of depolymerase as an effective treatment strategy other than antibiotics for K. pneumoniae infections. Furthermore, the project also aims to subtyping the K47 K. pneumoniae based on their depolymerase specificity. The represent strains of all K47 K. pneumoniae subtypes were conducted phylogenetic analysis using high throughput sequencing. The phylogenetic relationship of K47 K. pneumoniae subtypes combined with phage-derived depolymerases specificity were further analyzed. The acquire data will help in identifying the key gene or gene regions for determining the depolymerase specificity to reveal the molecular mechanisms governing the depolymerases specificity against K47 K. pneumoniae. Overall, the research outcomes from the proposed project will help in developing more efficient personalized treatments for drug-resistant K. pneumoniae infections.