摘要
      目前，在饮用水供应系统（DWSS）的每个部分都检测到了细胞内抗生素耐药性基因（iARGs）。尽管如此，细胞外抗生素耐药性基因（eARGs）缺乏DWSS的研究，这对抗生素耐药性的传播至关重要，并对人类健康构成潜在威胁。本研究旨在调查DWSS中eARGs的污染水平和变化趋势，并分析其原因和影响因素。在这里，从2019年10月到2021年7月，对原水、过滤水、饮用水处理厂的成品水、四个配电网站点的自来水以及配电系统不同层的生物膜进行了采样和分析。我们发现，氯化前的饮用水处理过程使eARGs的绝对丰度增加了8.64倍。相比之下，氯化消毒去除了大部分eARGs（平均去除率超过78.18%）。饮用水运输增加了eARGs的含量。自来水中总eARGs的绝对丰度（7.53×105–7.26×107拷贝/L）显著高于iARGs（2.63×105至3.26×106拷贝/L）（p<0.01，n=13），表明饮用水配水系统中eARGs污染比iARGs更严重。每个生物膜样品中总eARGs和总iARGs的相对丰度通常高于水样（分别为2.51倍和2.20倍）。因此，生物膜是eARGs和iARGs的培养箱。此外，DO、pH和微生物被发现是eARGs变化的重要驱动力。这项研究将有助于抗生素耐药性的风险评估和传播控制。
Abstract
At present, intracellular antibiotic resistance genes (iARGs) have been detected in every part of the drinking water supply system (DWSS). Still, the extracellular antibiotic resistance genes (eARGs) lack research in DWSS, which are essential in the spread of antibiotic resistance and pose a potential threat to human health. This study aims to investigate the pollution level and changing trends of eARGs in DWSS and to analyze the causes and influencing factors. Here, the raw water, the filtered water, the finished water from the drinking water treatment plant, the tap water from four distribution network sites, and the biofilm of different layers of the distribution system were sampled and analyzed from October 2019 to July 2021. We found that the drinking water treatment process before chlorination increased the total eARGs absolute abundance, up to 8.64 folds. In contrast, chlorination disinfection removed most eARGs (average removal rate of over 78.18%). The drinking water transportation increased the eARGs content. The absolute abundance of total eARGs (7.53 × 105–7.26 × 107 copies/L) in tap water was significantly higher than that of iARGs (2.63 × 105–3.26 × 106 copies/L) (p < 0.01, n = 13), indicating that the eARGs pollution was more severe than iARGs in drinking water distribution system. And the relative abundances of total eARGs and total iARGs in each biofilm sample were generally higher than those in water samples (2.51 folds and 2.20 folds, respectively). Hence the biofilm was an incubator of eARGs and iARGs. In addition, the DO, pH, and microorganisms were found as important driving forces for the change of eARGs. This study will be conducive to the risk evaluation and transmission control of antibiotic resistance.

https://www.sciencedirect.com/science/article/abs/pii/S0959652623008727