鄱阳湖区规模化养猪场废水中黏菌素及其质粒介导的耐药基因mcr-1的污染特征、相关性及影响因子研究

Polymyxins are regarded as the last-resort antibiotics for treatment of multidrug-resistant gram-negative bacterial infections in human being. However, their efficiency is seriously threatened by the discovery of plasmid-mediated colistin resistance gene mcr-1. Mcr-1 is widely spread in bacterium of the Enterobacteriaceae family isolated from various samples in 35 different countries and areas all over the world. Large amounts of colistin sulfate are released into environment through animal feces in China each year, which might not only result in pollution, but also promote the formation and horizontal gene transmission of mcr-1 in environment. Poyang Lake in Jiangxi Province, the largest freshwater lake in china, is a world famous wetland. There are lots of pig farms around the lake producing large quantities of wastewater with antibiotics and ARGs, which are very likely to flow into the lake and threaten its ecological environment. However, relative reports are rare, and data analyses are based on samples collected from only one pig farm. In this study, non-culture-based method and LC-MS/MS are to be applied to firstly investigate the pollution characteristics, correlation and impact factors of colistin sulfate and mcr-1 in wastewater from large-scale pig farms in Poyang Lake Area. The results may provide basis for assessing their ecological risk in Poyang lake, and for lowering their pollution level and the risk of transferring to human being, in turn to guarantee ecological safety of Poyang Lake and human health.

多粘菌素类药物被认为是抵御多重耐药革兰氏阴性菌感染的“最后一道防线”。但质粒介导的黏菌素耐药基因mcr-1的发现，使其有效性受到严重威胁。目前mcr-1已在全球35个不同国家和地区的不同来源肠杆菌科细菌中广泛传播。我国每年都有大量硫酸黏菌素经动物粪便排泄进入环境，在造成污染的同时，还可能会促进mcr-1在环境中的产生和水平传播。江西鄱阳湖是我国第一大淡水湖，世界著名湿地。环湖区域内养猪场密度高，废水中的抗生素及ARGs极可能汇入湖内，威胁其生态环境。但相关研究极少，且仅对个别猪场采样分析。本项目拟采用非培养法结合LC-MS/MS法，首次研究国际重要湿地鄱阳湖区猪场废水中硫酸黏菌素及mcr-1污染特征，结合相关性研究，为评估二者生态风险提供数据支撑；并探讨二者影响因子，为降低其污染水平、减小mcr-1传播至人类的风险提供实验基础。研究结果对保障鄱阳湖生态安全及人类健康具有重要意义。

多粘菌素类药物被认为是抵御多重耐药革兰氏阴性菌感染的“最后一道防线”。但质粒介导的黏菌素耐药基因mcr-1的发现，使其有效性受到严重威胁。目前mcr-1已在全球60多个不同国家和地区的不同来源肠杆菌科细菌中广泛传播。我国每年都有大量硫酸黏菌素经动物粪便排泄进入环境，在造成污染的同时，还可能会促进mcr-1在环境中的产生和水平传播。江西鄱阳湖是我国第一大淡水湖，世界著名湿地。环湖区域内养猪场密度高，废水中的抗生素及ARGs极可能汇入湖内，威胁其生态环境。但相关研究极少，且仅对个别猪场采样分析。本项目首次研究国际重要湿地鄱阳湖区猪场废水中硫酸黏菌素及mcr-1污染特征、相关性、影响因子及消减方法。发现硫酸黏菌素阳性率为13.8%，残留水平为7.29~30.1 ng/mL；mcr-1阳性率为10.3%，绝对或相对丰度分别为3.99~106.14 copies/mL和4~8；未检测到硫酸黏菌素和mcr-1同时为阳性的样品。硫酸黏菌素在废水中的残留与mcr-1基因的污染无直接相关性。超声对mcr-1丰度有显著影响，其次是温度、加温时间，而紫外线照射对mcr-1的影响甚微；当超声时间为15min、在60℃条件下作用5min时，可使阳性样品中mcr-1的含量下降30.6%。30倍用量高铁酸钾在pH为7条件下反应10min，可有效降解硫酸黏菌素，降解率达98.93%，腐植酸对降解无显著影响，且降解产物对环境微生物安全无毒；21.26 mg/mL高铁酸钾铁（以Fe计为6 mg/mL）在pH为5、温度为60℃的条件下作用15min，可使阳性水样中mcr-1基因消减率达55%。但值得注意的是，在某些条件下，超声或高铁酸钾可促进mcr-1的增加。研究成果为了解硫酸黏菌素和mcr-1基因在猪场废水中的污染情况及有效控制其污染水平，减小mcr-1基因经环境传播至人类的机率，保障鄱阳湖生态安全及人类健康提供了科学依据。