PSM介导的甲氧西林耐药金黄色葡萄球菌达托霉素异质性耐药机制研究

达托霉素是目前临床治疗MRSA感染的重要药物，也是为数不多的万古霉素治疗失败补救药物之一。近年来，国外学者和本课题组均发现其在临床使用过程中出现达托霉素异质性耐药（hDAP）亚群，导致治疗失败，其机制尚不明确。最新研究发现，MRSA分泌的PSM肽可调控细菌膜脂质和胞外囊泡的分泌而影响达托霉素杀菌活性。我们前期也发现我国MRSA流行克隆中存在一定比例的hDAP菌株，且不同克隆菌株存在PSM肽分泌差异并影响其达托霉素敏感性。因此推测PSM肽分泌及转运差异极可能是MRSA hDAP的重要机制。本研究将在全国MRSA流调分型数据库基础上，通过群体谱分析，明确hDAP在不同MRSA克隆中的分布；采用基因敲除、质谱分析、囊泡抽提和透射电镜等技术，研究PSM及其转运系统Pmt（ABC型转运蛋白）在MRSA的hDAP中的作用，阐明MRSA的hDAP分子机制，为科学制订MRSA感染治疗方案提供新理论。

Daptomycin has been used as an important therapeutic agent against MRSA, and it is one of the limited salvage alternatives for MRSA infections following vancomycin failure. Recently, foreign researchers and our team observed the emergence of daptomycin heteroresistance (hDAP) during therapy, which led to treatment failure, but the mechanism is not clear. Recent studies described that PSMs produced by MRSA could regulate the release of membrane lipid and extracellular vesicles and then impact on daptomycin activity. We also found that hDAP strains were identified frequently in the predominant Chinese MRSA lineages, while PSM production were diverse in different clones and associated with daptomycin susceptibility. So, we hypothesize that the differences of PSMs production and transfer are important mechanisms for MRSA hDAP. This study aims to determine the distribution of hDAP in the MRSA lineages, by using population analysis profile with isolates from our previous typing database for national MRSA epidemiology study. We will study the role of PSM and its transporters Pmt (ABC transporters) in MRSA hDAP and unveil the heteroresistance mechanism, by using gene knockout, mass-spectrometric, extracellular vesicles extraction and transmission electron microscope technique. The result of this study will provide theoretical basis for developing effective treatment strategies for MRSA infections.