城市污水厂MCR-1基因及其携带菌的污染

研究了南京某城市污水处理厂MCR-1基因及其携带菌的污染特征，从MCR-1的分布特征、影响因素及MCR-1携带菌的耐药特征等方面综合评价.结果发现MCR-1随处理流程丰度下降，去除率达83.6%，但其相对丰度在出水中显著升高，剩余污泥中含有高浓度MCR-1，浓度达2.88×10¹²copies/L.粘菌素耐药菌同样沿处理流程逐渐降低，出水降至53CFU/mL，去除率达99.98%，但在剩余污泥中浓度高达2.04×10⁵CFU/mL.相关性分析发现MCR-1丰度与氨氮含量呈正相关，而相对丰度与COD、总氮和硝酸盐含量呈负相关.耐药特征分析表明曝气池（CAST、MSBR）和曝气生物流化池（ABFT）中MCR-1携带菌可耐受较高浓度粘菌素，且污水处理使MCR-1携带菌对粘菌素的耐受能力提高.表明污水处理流程不但无法完全去除MCR-1及其携带菌，且导致耐药性风险提高.本研究可为评价污水中以MCR-1为代表的超级抗性基因的环境风险提供参考.

The pollution of MCR-1and MCR-1hosting bacteria in municipal wastewater treatment plants

The study investigated the pollution characteristics of MCR-1and MCR-1hosting bacteria in a municipal wastewater treatment plant in Nanjing, China. Their distribution and influence factors, as well as antibiotic resistance characteristics, were comprehensively assessed. The results indicated that the MCR-1abundance decreased obviously along with the treatment process, with the reduction efficiency of 83.6%. However, its relative abundance increased significantly in the treated effluent. High amount of MCR-1was detected in biosolids, with concentration of up to 2.88×10¹² copies/L. On the other hand, the concentration of colistin resistant bacteria also decreased gradually along with the treatment process. Their concentration decreased to 53 CFU/mL in the final effluent, with the reduction efficiency of 99.98%, but up to 2.04×10⁵ CFU/mL were detected in biosolids. According to the correlation analysis, MCR-1abundance positively correlated with ammonia concentration, while the relative abundance of MCR-1showed negative correlation with COD, TN and NO₃^--N concentration. The antibiotic resistance characteristics analysis indicated that MCR-1hosting bacteria in the activated sludge system (CAST and MSBR) and aeration biological fluid tank (ABFT) were tolerant to significantly higher colistin concentration relative to other sites. Additionally, the level of MCR-1hosting bacteria tolerant to colistin was enhanced by the treatment process, which implied that the wastewater treatment process could not completely reduce MCR-1 and MCR-1hosting bacteria, and even lead to the increase of their potential risks. The study will provide implications for assessing the environmental risks of MCR-1represented super antibiotic resistant genes.