南京地区污水厂、自来水厂及长江中抗性基因MCR-1和NDM-1的污染特征

近年来，新型抗性基因以其易传播和耐药广等特性，展现出比传统抗性基因更严峻的健康风险，在临床卫生领域受到广泛关注，但目前对其在环境中的行为和风险研究很少.为此，考察了2种有代表性的新型抗性基因MCR-1和NDM-1的污染特征，并借助荧光定量PCR探索了长江下游（南京段）及附近污水厂和自来水厂中MCR-1和NDM-1的分布特征，进而采用RDA（冗余性分析）评价了分布特征受水质指标的影响效果.结果表明:①污水厂进水中MCR-1和NDM-1绝对丰度较高，且随处理流程呈下降趋势，总去除率分别为92.5%和92.7%，但出水中MCR-1和NDM-1绝对丰度仍分别达2.5×108和7.0×106 copies/L.②长江下游（南京段）各采样点MCR-1和NDM-1绝对丰度的范围分别为8.5×107~3.5×109和4.3×105~2.1×107 copies/L，随水流方向呈降低趋势，但在个别采样点出现异常升高的情况，主要受该区域人为污染的影响.③自来水厂处理工艺对MCR-1和NDM-1去除率分别为75.0%和70.6%，但出水中存留的MCR-1和NDM-1绝对丰度分别达1.4×107和6.3×104 copies/L，且MCR-1和NDM-1在排泥水中大量富集.④MCR-1绝对丰度与ρ（COD_Cr）、ρ（NH₃-N）、电导率呈正相关，而NDM-1绝对丰度仅和浊度存在弱相关关系，与其他水质指标无明显相关性.研究显示，污水处理工艺无法有效去除MCR-1和NDM-1，大量抗性基因通过污水厂出水排入长江，同时自来水厂以含有较高绝对丰度抗性基因的长江水作为水源水，最终自来水厂出水中残存的抗性基因可能进入人体，生态健康风险较大. 

Pollution Characteristics of MCR-1 and NDM-1 in Wastewater Treatment Plants, Waterworks and Yangtze River of Nanjing Section

In recent years, some novel antibiotic resistance genes (ARGs) have shown more severe health risks than traditional ARGs because of their easy transmission and broad drug resistance. These emerging ARGs have received extensive attention in clinical health, but little research on the environmental impacts of them is conducted. This study examined the contamination characteristics of two typical emerging ARGs, MCR-1 and NDM-1. Quantitative PCR (QPCR) was used to explore the distribution of the two ARGs in the downstream of the Yangtze River (Nanjing section) and nearby wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). Redundancy analysis (RDA) was then adopted to evaluate the influence of water quality indicators on the distribution of the ARGs. The results showed that:(1) In the WWTPs, high concentrations of MCR-1 and NDM-1 in the plant influent were detected and the concentrations decreased in the wastewater treatment processes. The total removal efficiencies were 92.5% and 92.7% for the two ARGs respectively, but the concentrations still reached 2.5×10⁸ and 7.0×10⁶ copies/L in the effluent. (2) In the Yangtze River (Nanjing section), the concentration of the two ARGS were 8.5×10⁷-3.5×10⁹ and 4.3×10⁵-2.1×20⁷ copies/L respectively, which decreased with the direction of water flow, but increased abnormally at some sampling sites, which could be attributed to the anthropogenic pollutions in the area. (3) In the DWTPs, the removal efficiencies of the two ARGs were 75.0% and 70.6% respectively, but the concentrations of the ARGs were 1.4×10⁷ and 6.3×10⁴ copies/L of in the treated water. They were also greatly enriched in the sludge. (4) The concentration of MCR-1 was positively correlated with COD_Cr, NH₃-N and Turbidity. By comparison, NDM-1 was only weakly correlated with turbidity, but showed no significant correlation with other water quality indicators. The study indicated that the wastewater treatment processes could not effectively remove MCR-1 and NDM-1. A large amount of ARGs was discharged into the Yangtze River (Nanjing section) through the effluent. The Yangtze River (Nianjing section) with high concentration of the ARGs was used by the DWTPs as the source of drinking water, and the residual ARGs in the treated drinking water could cause great ecological and health risks.