Department of Civil, Environmental & Geomatic Engineering, University College London, London, WC1E 6BT, UK.
Department of Civil, Environmental & Geomatic Engineering, University College London, London, WC1E 6BT, UK.
Water Res. 2020 Sep 1;182:115954. doi: 10.1016/j.watres.2020.115954. Epub 2020 May 22.
Antibiotic resistance genes (ARGs) are being detected in drinking water frequently, constituting a major public health issue. As a typical drinking water treatment process, the biofilter may harbour various ARGs due to the filter biofilms established during the filtration process. The objective of this study was to investigate the behaviour of ARGs (bla, bla, bla, ermB, tetA, tetG, tetQ, tetW, tetX, sul 1, sul 2, dfrA1 and dfrA12) and their possible association with bacteria in a bench-scale biofiltration system. The impact of filter media on horizontal gene transfer (HGT) was also explored using a model conjugative plasmid, RP1. The biofiltration system comprised four types of biofilters, including sand, granular activated carbon (GAC), GAC sandwich, and anthracite-sand biofilters. Results showed that although the absolute abundance of ARGs decreased (0.97-log reduction on average), the ARGs' abundance normalised to bacterial numbers showed an increasing trend in the filtered water. Biofilms collected from the surface layer revealed the lowest relative abundance of ARGs (p < 0.01) compared to the deeper layer biofilms, indicating that the proportion of ARG-carrying bacteria was greater in the lower position. Most chosen ARG numbers correlated to Proteobacteria, Acidobacteria and Nitrospirae phyla, which accounted for 51.9%, 5.2% and 2.0% of the biofilm communities, respectively. GAC media revealed the highest transfer frequency (2.60 × 10), followed by anthracite (5.31 × 10) and sand (2.47 × 10). Backwashing can reduce the transferability of RP1 plasmid significantly in biofilms but introduces more transconjugants into the planktonic phase. Overall, the results of this study could enhance our understanding of the prevalence of ARGs in drinking water biofiltration treatment.
抗生素耐药基因（ARGs）经常在饮用水中被检测到，构成了一个主要的公共卫生问题。作为一种典型的饮用水处理工艺，生物滤池由于在过滤过程中形成的滤膜生物而可能含有各种 ARGs。本研究的目的是研究 ARGs（bla、bla、bla、ermB、tetA、tetG、tetQ、tetW、tetX、sul1、sul2、dfrA1 和 dfrA12）的行为及其与细菌的可能相关性在一个台式生物过滤系统中。还使用模型共轭质粒 RP1 探索了过滤介质对水平基因转移（HGT）的影响。生物过滤系统包括四种类型的生物滤池，包括砂、颗粒活性炭（GAC）、GAC 夹层和无烟煤-砂生物滤池。结果表明，尽管 ARGs 的绝对丰度降低（平均减少 0.97 个对数），但过滤水中 ARGs 的丰度归一化至细菌数量呈增加趋势。与深层生物膜相比，从表面层收集的生物膜显示出最低的 ARG 相对丰度（p<0.01），这表明较低位置携带 ARG 的细菌比例更大。大多数选定的 ARG 数量与变形菌门、酸杆菌门和硝化螺旋菌门相关，分别占生物膜群落的 51.9%、5.2%和 2.0%。GAC 介质显示出最高的转移频率（2.60×10），其次是无烟煤（5.31×10）和砂（2.47×10）。反冲洗可以显著降低生物膜中 RP1 质粒的可转移性，但会将更多的转导子引入浮游相中。总体而言，本研究的结果可以增强我们对饮用水生物过滤处理中 ARG 流行率的理解。
