多重耐药性大肠杆菌的水体污染行为及细菌粘附迁移机制研究

The contamination and control of antibiotic resistant bacteria in water cycle is one of the key research themes in the discipline of water quality engineering. Recent studies reported that huge amounts of antibiotics, antibiotic resistant bacteria and genes have been discharged into the aquatic environments, which may result in negative impacts on the integrity of water ecosystem and safe water utilization. Much research interest has focused on the ecotoxicological behavior of the discharged antibiotics and antibiotic resistant genes. However, the studies on the pollution behavior, i.e. survival, transport and fates, of these antibiotic resistant bacteria in the receiving water bodies have not been carried out. Antibiotic resistant bacteria not only spread the antibiotic resistant genes and elevate the overall antibiotic resistance in the ecosystem, possibly cultivating the so-called superbugs, but also cause water-borne diseases that could not be cured by the conventional chemotherapies. According to biological mechanisms of antibiotic resistance, the viability, transport property and pathogenicity in water will probably be altered when bacteria acquire their antibiotic resistance, which might further affect the strategy used to control microorganisms in healthy water cycle management. This project will investigate the influence of multi-drug resistant Escherichia coli strains on water ecology safety and risk assessment, and on water quality. From the aspects of microbial activity, antibiotic resistance and microbe-substrate interactions, the dynamics and kinetics of microbial survival and transport in the subsurfaces will be studied. We expect that the transport behavior and fates of multi-resistant E. coli in water environment will be elucidated. Some important issues, i.e. if bacteria change their transport properties when they acquire antibiotic resistance, and if a specific resistant bacterium poses more negative impacts on the safety water environment, are to be addressed by this research. The outcome of this research will provide a scientific basis for water pollution control and evaluation of water utilization in the scenario of discharges of antibiotic resistant bacteria into aquatic environment.

耐药性细菌是社会水循环过程中病原微生物污染与控制的重要研究内容。研究显示人类向水体排放大量抗生素、耐药性病原菌和基因。现有相关研究多集中于抗生素污染和耐药性基因的生态毒理学影响，忽视了耐药性细菌的水体污染行为。耐药性细菌不仅可作为基因传播载体提升水体微生物整体耐药性水平，增大“超级细菌”出现的风险，还可以水为媒介直接引起抗生素无效的疾病，威胁用水安全。根据耐药性的生物学机理，细菌在水中的活性、扩散迁移和致病性等特征可能由于获得耐药性而产生变化，从而改变原有健康水循环过程中微生物污染的控制策略。项目将首次针对水中耐药性细菌排放产生的水污染新问题，以多重耐药性大肠杆菌为研究对象，以“细菌-水-环境介质”微界面的粘附迁移机制为核心，从细菌的耐药性、活性和扩散迁移性三方面，考察多重耐药性细菌在水中的迁移转化过程及水质影响。研究结果为耐药性细菌排放条件下水体污染控制与用水安全评价提供理论依据。

多重耐药性细菌是社会水循环过程病原微生物污染与控制的重要研究内容之一。本项目以多重耐药性大肠杆菌为研究对象，以“细菌-水-环境介质”微界面的粘附迁移机制为核心，从细菌的耐药性、活性、扩散迁移性、耐药性暴露风险评价四方面，考察多重耐药性细菌在水中的迁移转化过程及水质影响，研究结果为耐药性细菌排放条件下水体污染控制与用水安全评价提供理论依据。通过本项目研究得到以下结论：.（1）城市降雨径流、城市娱乐景观水体、城市固体废物管理设施、城乡畜禽养殖废物处理设施等诸多环节向水环境排放大量多重耐药性大肠杆菌，它们对临床常用的很多抗生素都具有较高的耐受性。.（2）抗生素耐药性大肠杆菌在某些耐药性基因表达过程中会改变细菌的表面化学组成与细胞结构，进而改变细胞的表面特性，对细菌在环境颗粒介质表面的粘附和迁移行为产生影响。.（3）在本项目取样监测的城市娱乐景观水体范围内，再生水回用做景观水体补水并未明显提高水体中大肠杆菌的浓度水平和耐药性水平。.（4）耐药性细菌在再生水中停留时间的延长会降低细菌活性，同时影响其在水环境颗粒介质表面的粘附行为，进而影响其在水体中的迁移扩散和最终归宿。此外，细菌在石英砂、黏土和沸石等颗粒物表面的粘附性能受离子强度、抗生素培养条件、菌株和介质种类等因素影响。.（5）Ohshima软颗粒电泳理论能够较好地模拟多重耐药性大肠杆菌表面的柔性物化性质，在抗生素存在条件下多重耐药大肠杆菌表面柔性有所增大。.（6）用于细菌灭活性能表征的单一性指标，不能准确评价细菌在消毒剂作用下的失活程度，包含多维度细胞生理参数的综合评价指标开发对环境微生物研究具有重要意义。在耐药性基因污染的背景下，耐药性病原菌灭活的程度要求也是一个值得关注的问题。