动物源大肠杆菌中oqxAB多重耐药质粒的形成机制及抗菌药对其在菌群中持久性的影响

Plasmids play an important role in the rapid dissemination of multidrug resistance (MDR). The emergence of some new MDR plasmids conferring resistances to most first-line antibacterial agents, and whether these MDR plasmids are able to successfully persist in bacterial populations, substantially affect the results of the treatment and control of most bacterial infections. Multidrug efflux pump OqxAB, a new member of plasmid-mediated quinolone resistance (PMQR), with a wide substrate specificity, disseminates widely and has attracted much attention from the researchers around the world. MDR plasmids carrying oqxAB has been found in Enterobacteriaceae recently, however, in E. coli, with a more complex evolutionary process of antibiotic resistance, many questions about the oqxAB-MDR plasmids remain unanswered. This project intends to: investigate the epidemiological characteristics of the oqxAB-MDR plasmids among E. coli isolates from animals, and identify the prevalence and dissemination mechanism of these plasmids in pathogens of animal origin; clarify the molecular development mechanism of the newly formed oqxAB-MDR plasmids and compare the evolutionary relationships of these plasmids from different animal origins using high-throughput sequencing; and assess the ability of the new plasmids to survive in bacterial populations and the impact of antibacterial drugs on this ability. This study will provide not only the foundation for risk assessment of the development of MDR plasmids under the antibiotics pressure, but also the instruction for preventing the increasing prevalence of MDR plasmids.

质粒对多重耐药的快速传播发挥着重要的作用，特别是一些新多重耐药质粒，它们能否在菌群中持久存在，更关系到许多临床感染性疾病治疗的成败。多重耐药外排泵OqxAB是一新的质粒介导喹诺酮耐药家族成员，由于其具有广泛的底物谱且分布范围很广，因而成为世界各地耐药性监控的重要对象和研究热点。最近发现携带oqxAB的多重耐药质粒已在肠杆菌中出现，但在耐药进化更复杂的大肠杆菌中，关于这一质粒的众多问题尚无解释。本项目拟开展动物源大肠杆菌中oqxAB多重耐药质粒的流行特征研究，明确该质粒在我国动物源细菌中的流行情况和传播机制；采用高通量测序分析主要的新oqxAB多重耐药质粒的遗传图谱，阐明质粒的形成机制及其在不同来源菌株间的亲缘关系；并评估新oqxAB多重耐药质粒能否在菌群中持久存在及抗菌药对其影响。本研究将为评估在抗菌药压力下，多重耐药质粒形成的风险提供依据，也为有效防控多重耐药质粒的流行提供理论指导。

携带oqxAB的多重耐药质粒可介导细菌对多种抗菌药耐药，新出现的oqxAB多重耐药质粒能否在菌群中持久存在，关系到许多临床感染性疾病治疗的成败。本项目研究了我国动物源大肠杆菌中oqxAB多重耐药株和质粒的流行特征、oqxAB多重耐药质粒的传播与形成机制和抗菌药等对其在菌群中持久性的影响。结果显示我国动物源大肠杆菌多重耐药十分严重，同时携带oqxAB和blaCTX-M的多重耐药株最为流行，其中以同时携带oqxAB-mcr-1-blaCTX-M的多重耐药株最为常见; 研究发现，不同地区的大肠杆菌中oqxAB-mcr-1-blaCTX-M-fosA3的连锁传播是由结构相似的IncHI2/ST3型质粒介导的，这也是造成oqxAB多重耐药株和mcr-1多重耐药株快速传播的一个重要原因，oqxAB-blaCTX-M的连锁传播是由结构相似的IncHI2/ST3 质粒和进化多样的F33:A-:B-型质粒介导的；IS26等插入序列在同时携带oqxAB-mcr-1-blaCTX-M-fosA3的多重耐药质粒的形成中发挥重要作用；同时携带oqxAB-mcr-1-blaCTX-M-fosA3的IncHI2/ST3型多重耐药质粒pWF5-29对宿主菌有一定的适应性代价，但通过敏感菌亚抑菌浓度的头孢噻肟和多黏菌素均可分别消除其适应性代价，显著提高宿主菌的竞争优势。且随着时间的延长（96h），多黏菌素的影响有增强的趋势。敏感菌亚抑菌浓度不同梯度的头孢噻肟、多黏菌素和纳米材料可分别对pWF5-29的接合转移效率产生不同影响，其中各亚抑菌浓度的多黏菌素、0.5mmol/L的纳米氧化铝和0.05mmol/L的纳米氧化锌均可显著增加pWF5-29的接合转移效率。本项目的研究结果探明了我国动物源大肠杆菌中oqxAB多重耐药质粒的流行特征、传播与形成机制和抗菌药等对其在菌群中持久性的影响，从而综合评估环境中抗菌药物和纳米材料污染对该质粒未来趋势的影响，这些研究成果为有效防控多重耐药质粒的流行提供了理论借鉴。