新生儿肠道外致病性大肠杆菌的流行特征及变异进化规律研究

The extraintestinal pathogenic Escherichia coli (ExPEC) is the main pathogen causing severe infectious diseases such as neonatal sepsis and purulent meningitis. Due to insufficient knowledge, there is still lack of effective prevention and control measures. Previous reports and pre-research studies have shown that there are significant differences in drug resistance phenotypes and virulence factors between ExPEC and intestinal pathogenic E. coli. Accurately understanding the epidemiological distribution, drug resistance, virulence characteristics and evolution rules of ExPEC is the key to grasp public health hazards timely, conduct risk assessment and formulate reasonable control measures. However, the incidence, epidemiological and pathogenic characteristics of neonatal ExPEC is less attention in the worldwide. Based on the platform of Beijing Children's Hospital Group, we will collect neonatal ExPEC strains from the different regions of the country to explore the epidemiological characteristics of the infection. We will select the representative ExPEC strains of the whole genome sequencing and informatics analysis to reveal the molecular basis of ExPEC pathogenesis and tclarify the role of gene recombination, insertion/deletion and horizontal gene transfer in the evolution of virulence and drug resistance. Additionally, the neonatal ExPEC evolution and phylogenetic relationships will be elucidated by the phylogenetic analysis and population structure reconstruction in order to provide new targets and strategies for controlling the neonatal ExPEC infections and clinical interventions.

肠道外致病性大肠杆菌（ExPEC）是引起新生儿败血症和化脓性脑膜炎等严重感染的主要病原菌，因对其认识不足，当前仍缺乏有效的防控措施。既往报道和课题前期研究提示ExPEC在耐药表型、毒力因子等方面与肠道内致病性大肠杆菌差异明显。准确了解ExPEC的流行分布、耐药和毒力特点及其传播进化规律，才能及时掌握其公共卫生危害、开展风险评估和制定合理的控制措施，但国内外罕见新生儿ExPEC的发病情况、流行特点和病原学的系统研究。课题基于北京儿童医院集团平台，拟在全国不同地区收集新生儿ExPEC菌株，探讨其感染流行特征；通过代表性菌株全基因组测序及信息学分析，揭示新生儿ExPEC致病的分子基础，阐明基因重组、插入/缺失、水平转移等遗传事件在其毒力和耐药及其进化中的作用；通过系统发生分析与种群结构重建，探讨新生儿ExPEC演化规律及亲缘性关系，为控制新生儿ExPEC感染、临床干预提供新的靶点和策略。

肠道外致病性大肠杆菌是引起新生儿败血症和化脓性脑膜炎等严重感染的主要病原菌，当前仍缺乏有效的防控措施。本研究通过对收集的7家三级甲等医院住院新生儿大肠杆菌临床分离株进行研究，探讨新生儿大肠杆菌菌株的流行病学特征、耐药特点、毒力因子特征、分子分型及遗传多态性和进化规律。抗生素药物敏感性试验显示：新生儿大肠杆菌菌株对抗生素耐药严重，多重耐药率高。产ESBLs大肠杆菌菌株对头孢菌素、氨曲南等耐药率明显高于非产ESBLs菌株。毒力因子分布：fimH、iutA、kspM II、fyuA检出率最高，产ESBLs菌株iutA、fimH、fyuA、kspM Ⅱ阳性率较高。利用MLST分子分型，探究大肠杆菌菌株的遗传多态性，主要的MLST型别为ST1193、ST95、ST73、ST410和ST131，其中ST1193、ST95最为多见。不同ST型别大肠杆菌菌株的耐药情况不同，ST1193、ST410、ST131产ESBL率及多重耐药率均明显高于ST95、ST73。基于chu A、yja A 基因和TSPE4.C2 片段相结合的三重PCR 技术探讨大肠杆菌菌株的进化规律，其中B2群占比最多，其次为D群、A群和B1群。通过PFGE分型及全基因组测序分析，揭示大肠杆菌菌株间的同源性及母子的亲缘关系十分密切。应用全基因组测序对耐药显著的大肠杆菌菌株进行分析，大肠杆菌菌株携带的耐药基因数目不等，共含有7类抗生素的28个不同耐药基因。抗生素检出率前三位分别是氨基糖苷类、β-内酰胺类和复方磺胺类。耐药基因数目最多的是β-内酰胺类的blaTEM-1B。综上，重视并加强新生儿大肠杆菌流行病学监测，准确了解耐药和毒力特点以及同源性、亲缘性等流行学特征，才能预测传播进化规律，开展风险评估和制定合理的防控措施。本研究对于新生儿大肠杆菌菌株的检测及监测、溯源传播来源、进化研究、临床抗菌药物的合理使用及防控均具有重要指导意义。