摘要
      大型污水处理厂每年向地表水中排放数百吨总悬浮固体。此外，在联合下水道系统的情况下，暴雨期间下水道溢流释放的量相当。随着沉降，附着颗粒的微生物及其抗生素抗性基因（ARGs）随之被输送到接收水的河床。为了更好地了解这一过程的动力学，在间歇反应器中加入了一种颗粒废水部分，该反应器之前充满了天然河流沉积物和自来水。同时，对抗生素（AB）（红霉素、四环素、环丙沙星、罗红霉素、青霉素V和磺胺甲恶唑）进行加标，以研究其选择耐药性的能力。使用定量PCR对水中和沉积物中六种ARG（ermB、tetM、blaTEM、sul1、CTX-M-32和qnrS）以及总细菌（16S rDNA）的丰度进行了为期两个月的监测。尽管连续暴露于AB（每个5μg/L），但ARGs的丰度仍然不受影响。废水颗粒的添加导致水中（3-5个对数单位）和沉积物（1-4个对数单位。我们的研究结果表明，受纳河流中ARG丰度的增加是污水处理厂排放或下水道溢流事件中ARG持续输入的结果。它们进一步表明，如果去除这种持续输入，ARG的升高不会在接收河流中持续存在。鉴于在本地人口中观察到稳定的ARGs背景浓度，这似乎仅适用于废水引入的ARGs。
Abstract
Large-scale wastewater treatment plants (WWTPs) discharge hundreds of tons of total suspended solids (TSS) into surface waters every year. Additionally, a comparable amount is released by sewer overflows during heavy rain events in case of combined sewer systems. Along with sedimentation, particle-attached microorganisms and their antibiotic resistance genes (ARGs) are herewith transported to the riverbed of the receiving water. To better understand the dynamics of this process, a particulate wastewater fraction was added into batch reactors, which were previously filled with natural river sediments and tap water. In parallel, antibiotics (ABs) (erythromycin, tetracycline, ciprofloxacin, roxithromycin, penicillin V, and sulfamethoxazole) were spiked to investigate their capability to select for resistance. The abundance of six ARGs (ermB, tetM, blaTEM, sul1, CTX-M-32, and qnrS) as well as total bacteria (16S rDNA) was monitored in waters and in sediments for a duration of two months using quantitative PCR. Despite a continuous exposure to ABs (5 μg/L each), the abundance of ARGs remained unaffected. Addition of wastewater particles resulted in a sudden and strong increase of ARGs in waters (3–5 log units) and sediments (1–4 log units), however, elevated ARGs underwent a particular and complete decay. Our results indicate that the increased ARG abundances in receiving rivers are the result of a continuous import of ARGs from WWTP discharges or sewer overflow events. They further imply that elevated ARGs do not persist in receiving rivers, if this continuous import is removed. This seems to be the case merely for ARGs introduced by wastewater, given that a stable background concentration of ARGs was observed for the native population.

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