群体感应系统对铜绿假单胞菌异质性耐药的调控作用研究

“Heteroresistance” describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic. Since more resistant subpopulations may be selected during antimicrobial therapy, heteroresistance is a risk factor for development of antibiotic resistance and causes treatment failure. However, the poor understanding in profiles and molecular mechanisms of heteroresistance precludes evaluating the clinical magnitude and severity of this phenomenon. Here, we found the Pseudomonas aeruginosa (P. aeruginosa) clinical isolates displayed frequent carbapenem (meropenem)-heteroresistance, which was related to down-regulated expression of quorum sensing (QS) genes lasI/rhlI, indicated that QS may be the important mechanisms underlying heteroresistance. Based on this, our researches will focus on: 1) characterizing the heteroresistance profiles of P. aeruginosa clinical isolates; 2) clarifying the roles of QS in heteroresistance and its underlying mechanism; 3) exploring the regulation function of QS in heteroresistance between different species. Our findings may provide new insight into the regulatory networks of heteroresistance, and offer novel potential targets for preventing antibiotic resistance.

异质性耐药是导致临床抗感染治疗失败及细菌产生耐药性的重要危险因素，目前对其现状和机制缺乏全面认识。课题组发现临床分离的铜绿假单胞菌对美罗培南异质性耐药现象严重，异质性耐药阳性菌中群体感应系统(QS)关键基因lasI、rhlI表达显著下调，敲除以上基因导致铜绿假单胞菌异质性耐药增强，提示QS系统可能调控铜绿假单胞菌异质性耐药。已知QS系统基因表达与环境变化密切相关，因此，我们假设，抗生素作用下，铜绿假单胞菌QS系统表达下调，菌群生长去同步化，单克隆来源的细菌向不同耐药能力分化，是异质性耐药发生的重要机制。在前期基础上，课题拟以QS系统为突破口，研究①临床上铜绿假单胞菌对常用抗生素的异质性耐药现状；②阐明QS系统对铜绿假单胞菌异质性耐药的调控作用及机制；③探索铜绿假单胞菌QS信号分子能否调控其它种类细菌的异质性耐药，从而揭示细菌异质性耐药的机制，为指导临床合理用药和减少细菌耐药的发生提供依据。

异质性耐药是导致临床抗感染治疗失败及细菌产生耐药性的重要危险因素，目前对其现状和机制缺乏全面认识。本研究前期发现临床分离的铜绿假单胞菌（P. aeruginosa）对美罗培南异质性耐药现象严重，异质性耐药阳性菌中群体感应系统(QS)关键基因lasI和rhlI的表达显著下调，敲除以上基因导致P. aeruginosa异质性耐药增强，提示QS系统可能调控P. aeruginosa异质性耐药。进一步通过本研究发现，临床上P. aeruginosa对常用抗生素阿米卡星、美罗培南、环丙沙星和头孢他啶均有不同程度的异质性耐药，且QS系统负调控P. aeruginosa的异质性耐药。在机制上，初步研究发现膜孔蛋白及外排泵相关基因的表达在异质性耐药菌株中发现明显改变，提示这些基因可能参与调控P. aeruginosa的异质性耐药，具体分子机制有待转录组测序结果验证。最后采用P. aeruginosa-大肠埃希菌共培养模型，探索P. aeruginosa能否通过QS系统调控其他种类细菌的耐药性，发现EC600对阿米卡星表现出异质性，且QS外源信号分子负调控EC600的异质性耐药。以上研究成果，明确了P. aeruginosa对临床常用抗生素异质性耐药的基本现状，阐明了QS系统对P. aeruginosa异质性耐药的调控作用及机制，并探讨了P. aeruginosa通过QS系统影响其它种类细菌耐药性的作用，为指导临床合理用药和减少细菌耐药的发生提供科学依据。