Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters - Research and Management, 6047 Kastanienbaum, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Aquatic Ecology, 6047 Kastanienbaum, Switzerland.
Environ Int. 2015 Aug;81:45-55. doi: 10.1016/j.envint.2015.04.005. Epub 2015 Apr 24.
Antibiotic resistance genes (ARGs) are emerging environmental contaminants, known to be continuously discharged into the aquatic environment via human and animal waste. Freshwater aquatic environments represent potential reservoirs for ARG and potentially allow sewage-derived ARG to persist and spread in the environment. This may create increased opportunities for an eventual contact with, and gene transfer to, human and animal pathogens via the food chain or drinking water. However, assessment of this risk requires a better understanding of the level and variability of the natural resistance background and the extent of the human impact. We have analyzed water samples from 21 Swiss lakes, taken at sampling points that were not under the direct influence of local contamination sources and analyzed the relative abundance of ARG using quantitative real-time PCR. Copy numbers of genes mediating resistance to three different broad-spectrum antibiotic classes (sulfonamides: sul1, sul2, tetracyclines: tet(B), tet(M), tet(W) and fluoroquinolones: qnrA) were normalized to copy numbers of bacterial 16S rRNA genes. We used multiple linear regression to assess if ARG abundance is related to human activities in the catchment, microbial community composition and the eutrophication status of the lakes. Sul genes were detected in all sampled lakes, whereas only four lakes contained quantifiable numbers of tet genes, and qnrA remained below detection in all lakes. Our data indicate higher abundance of sul1 in lakes with increasing number and capacity of wastewater treatment plants (WWTPs) in the catchment. sul2 abundance was rather related to long water residence times and eutrophication status. Our study demonstrates the potential of freshwater lakes to preserve antibiotic resistance genes, and provides a reference for ARG abundance from lake systems with low human impact as a baseline for assessing ARG contamination in lake water.
抗生素耐药基因（ARGs）是新兴的环境污染物，已知通过人类和动物的粪便不断排放到水生环境中。淡水水生环境代表了 ARG 的潜在储存库，并可能允许污水衍生的 ARG 在环境中持续存在和传播。这可能会增加通过食物链或饮用水最终接触和基因转移到人类和动物病原体的机会。然而，评估这种风险需要更好地了解自然耐药背景的水平和可变性，以及人类影响的程度。我们分析了来自瑞士 21 个湖泊的水样，这些水样取自不受当地污染源直接影响的采样点，并使用定量实时 PCR 分析了 ARG 的相对丰度。介导对三种不同广谱抗生素类别的耐药性的基因（磺胺类：sul1、sul2、四环素类：tet(B)、tet(M)、tet(W)和氟喹诺酮类：qnrA）的拷贝数被归一化为细菌 16S rRNA 基因的拷贝数。我们使用多元线性回归来评估 ARG 丰度是否与流域中的人类活动、微生物群落组成和湖泊的富营养化状况有关。在所采样的湖泊中均检测到了 sul 基因，而仅有四个湖泊中存在可量化数量的 tet 基因，并且在所有湖泊中 qnrA 仍未检出。我们的数据表明，在流域中废水处理厂（WWTP）数量和处理能力增加的湖泊中，sul1 的丰度更高。sul2 的丰度与水停留时间长和富营养化状况有关。我们的研究表明，淡水湖泊有潜力保留抗生素耐药基因，并为低人为影响的湖泊系统中的 ARG 丰度提供了一个参考，作为评估湖泊水中 ARG 污染的基线。
