Antimicrobial resistance is a well-documented public health concern. The role that drinking water distribution pipes have as sources of antibiotic resistance genes (ARGs) is not well known. Metals are a known stressor for antibiotic resistance development, implying that aging metal-pipe infrastructure could be a source of ARGs. The objective of this study was to determine if ARGs, metal resistance genes (MRGs), and intI1 were pervasive across various pipe biofilm sample types (biomass surfaces, pipe surfaces, corrosion tubercles, and under corrosion tubercles) and if the resistance genes associated with particular microbial taxa. Eight sample types in triplicate (n = 24) were taken from inside a >100 year-old, six ft. section of a full-scale chloraminated cast iron drinking water main. Droplet digital PCR (ddPCR) was employed as a novel approach to quantify ARGs in pipes from full-scale drinking water distribution systems (DWDS) because it yielded higher detection frequencies than quantitative PCR (qPCR). Illumina sequencing was employed to characterize the microbial community based on 16S rRNA genes. ARGs and MRGs were detected in all 24 pipe samples. Every sample contained targeted genes. Interestingly, the mean absolute abundances of ARGs and MRGs only varied by approximately one log value across sample types, but the mean relative abundances (copy numbers normalized to 16S rRNA genes) varied by over two log values. The ARG and MRGs concentrations were not significantly different between sample types, despite significant changes in dominant microbial taxa. The most abundant genera observed in the biofilm communities were Mycobacterium (0.2–70%), and β-lactam resistance genes bla_TEM, bla_SHV, and the integrase gene of class 1 integrons (intI1) were positively correlated with Mycobacterium. The detection of ARGs, MRGs, and class 1 integrons across all sample types within the pipe indicates that pipes themselves can serve as sources for ARGs in DWDS. Consequently, future work should investigate the role of pipe materials as well as corrosion inhibitors to determine how engineering decisions can mitigate ARGs in drinking water that stem from pipe materials.

中文翻译：

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铸铁饮用水管生物膜支持多种微生物群落，其中包括抗生素抗性基因，金属抗性基因和1类整合素

抗菌素耐药性是有据可查的公共卫生问题。饮用水分配管道作为抗生素抗性基因（ARG）来源的作用尚不清楚。金属是导致抗生素耐药性发展的已知压力源，这意味着老化的金属管基础设施可能是ARG的来源。这项研究的目的是确定ARG，金属抗性基因（MRG）和intI 1是否遍及各种管道生物膜样品类型（生物质表面，管道表面，腐蚀结节以及在腐蚀结节下），以及这些抗性基因是否相关特别是微生物类群。一式三份的八种样品类型（n= 24）是从超过100年的，六英尺长的完整规模的氯化铸铁饮用水总管中采集的。液滴数字PCR（ddPCR）被用作定量全尺寸饮用水分配系统（DWDS）中管道中ARG的新方法，因为它产生的检测频率高于定量PCR（qPCR）。基于16S rRNA基因，Illumina测序被用来表征微生物群落。在所有24个管道样品中均检测到ARG和MRG。每个样品均包含靶向基因。有趣的是，ARG和MRG的平均绝对丰度在样品类型之间仅变化约一个对数值，但平均相对丰度（对16S rRNA基因标准化的拷贝数）变化超过两个对数值。样品类型之间的ARG和MRGs浓度无显着差异，尽管优势微生物类群发生了显着变化。在生物膜群落中观察到的最丰富的属是分枝杆菌（0.2–70％）和β-内酰胺抗性基因bla _TEM，bla _SHV和1类整合素整合酶基因（intI 1）与分枝杆菌呈正相关。在管道内所有样本类型中检测到ARG，MRG和1类整数表示管道本身可以用作DWDS中ARG的来源。因此，未来的工作应调查管道材料以及缓蚀剂的作用，以确定工程决策如何减轻源自管道材料的饮用水中的ARG。