① 再生水的耐药基因组有别于直饮水，sul1和部分样品中blaTEM, qnrA, intI1基因丰度高于直饮水；② 常规污水处理流程缺乏减灭抗生素耐药性的措施，水处理设施对大部分耐药基因（ARG）没有减灭作用；③ 193个ARG与质粒有关，说明水源ARG可通过水平基因转移进行扩散，基因转移元件在再生水中更普遍；④ 污水处理过程存在耐药性筛选压力，部分ARG丰度与供水系统中抗生素、金属和消毒剂浓度有关；⑤ 供水过程普遍降低ARG的多样性，但不影响ARG总丰度。
Metagenomic Characterization of Antibiotic Resistance Genes in Full-Scale Reclaimed Water Distribution Systems and Corresponding Potable Systems
Water reclamation provides a valuable resource for meeting nonpotable water demands. However, little is known about the potential for wastewater reuse to disseminate antibiotic resistance genes (ARGs). Here, samples were collected seasonally in 2014-2015 from four U.S. utilities' reclaimed and potable water distribution systems before treatment, after treatment, and at five points of use (POU). Shotgun metagenomic sequencing was used to profile the resistome (i.e., full contingent of ARGs) of a subset ( n = 38) of samples. Four ARGs ( qnrA, bla, vanA, sul1) were quantified by quantitative polymerase chain reaction. Bacterial community composition (via 16S rRNA gene amplicon sequencing), horizontal gene transfer (via quantification of intI1 integrase and plasmid genes), and selection pressure (via detection of metals and antibiotics) were investigated as potential factors governing the presence of ARGs. Certain ARGs were elevated in all ( sul1; p ≤ 0.0011) or some ( bla, qnrA; p ≤ 0.0145) reclaimed POU samples compared to corresponding potable samples. Bacterial community composition was weakly correlated with ARGs (Adonis, R = 0.1424-0.1734) and associations were noted between 193 ARGs and plasmid-associated genes. This study establishes that reclaimed water could convey greater abundances of certain ARGs than potable waters and provides observations regarding factors that likely control ARG occurrence in reclaimed water systems.
Emily Garner,Chaoqi Chen,Kang Xia,Jolene Bowers,David M Engelthaler,Jean McLain,Marc A Edwards,Amy Pruden