Overhead tank (OHT)-based gravity-fed water distribution systems are popular in many low and middle-income countries; yet, they are poorly characterized despite being notorious for water quality deterioration. We investigated the potential for antibiotic resistance and horizontal gene transfer in tap water as it traversed through a gravity-fed water distribution system with six interconnected OHTs. Tap water was sampled from nine buildings over three seasons (summer, monsoon and winter) to compare the water quality in OHTs vs. at the user-end. Antibiotic resistance genes (ARGs) (sul1, sul2, blaOXA-1, and ermF), class 1 integron-integrase gene (intI1), opportunistic pathogens (Legionella pneumophila and Mycobacterium avium), 16S rRNA gene copies, yccT (Escherichia coli) and water quality parameters were characterized. Tap water samples at the user-end indicated selection of intI1, which correlated with the levels of 16S rRNA gene copies (r = 0.79), sul1 (r = 0.77), Cu (r = 0.48) and nitrate (r = 0.28). The absolute levels of sul1, intI1, opportunistic pathogens, 16S rRNA gene copies, and heavy metals were generally higher at the user-end and during the warmer seasons. The tap water was highly corrosive and levels of Fe and Pb exceeded the WHO guidelines in 24/81 and 19/81 samples, respectively. Heavy metals, DWDS-specific factors, season of sampling, and nitrate correlated with the levels of sul1, intI1, and opportunistic pathogens in tap water at the user-end. The findings of this study expose the susceptibility of OHTs to selection of intI1 and suggest control of corrosion to limit the prevalence and levels of ARGs and opportunistic pathogens in tap water.

中文翻译：

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由基于高架水箱的配水系统供应的水中人为抗生素抗性标记的增加

基于高架水箱 (OHT) 的重力供水系统在许多低收入和中等收入国家很受欢迎；然而，尽管它们因水质恶化而臭名昭著，但它们的特征却很差。我们研究了自来水通过具有六个相互连接的 OHT 的重力供水分配系统时抗生素抗性和水平基因转移的潜力。自来水在三个季节（夏季、季风和冬季）从九个建筑物中取样，以比较 OHT与用户端的水质。抗生素抗性基因 (ARG)（sul 1、sul 2、bla OXA-1 和erm F）、1 类整合子-整合酶基因（int I1）、机会性病原体（嗜肺军团菌和鸟分枝杆菌）、16S rRNA 基因拷贝、yc cT（大肠杆菌）和水质参数进行了表征。用户端的自来水样本表明选择了int I1，这与16S rRNA基因拷贝（r = 0.79）、sul 1（r = 0.77）、Cu（r = 0.48）和硝酸盐（r = 0.28）的水平相关）。sul 1, int的绝对水平I1、机会性病原体、16S rRNA 基因拷贝和重金属在用户端和温暖季节普遍较高。自来水具有高度腐蚀性，24/81 和 19/81 样品中的 Fe 和 Pb 含量分别超过了 WHO 指南。重金属、DWDS 特定因素、采样季节和硝酸盐与用户端自来水中sul 1、int I1 和机会性病原体的水平相关。这项研究的结果揭示了 OHT 对int I1选择的敏感性，并建议控制腐蚀以限制自来水中 ARG 和机会性病原体的流行和水平。