Department of Public Health and Infectious Diseases, University of Rome "La Sapienza", Piazza A. Moro 5, 00185 Rome, Italy.
Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
Int J Environ Res Public Health. 2020 Sep 18;17(18):6813. doi: 10.3390/ijerph17186813.
Wastewater treatment plants (WWTPs) are microbial factories aimed to reduce the amount of nutrients and pathogenic microorganisms in the treated wastewater before its discharge into the environment. We studied the impact of urban WWTP effluents on the abundance of antibiotic resistance genes (ARGs) and antibiotic-resistant (AR-) in the last stretch of two rivers (Arrone and Tiber) in Central Italy that differ in size and flow volume.
Water samples were collected in three seasons upstream and downstream of the WWTP, at the WWTP outlet, and at sea sites near the river mouth, and analyzed for the abundance of ARGs by qPCR and AR- using cultivation followed by disk diffusion assays.
For all studied genes (, , , , , and ), absolute concentrations were significantly higher in the Tiber than in the Arrone at all sampling sites, despite their collection date, but the prevalence of target ARGs within bacterial communities in both rivers was similar. The absolute concentrations of most ARGs were also generally higher in the WWTP effluent with median levels between log 4 and log 6 copies per ml but did not show differences along the studied stretches of rivers. Statistically significant site effect was found for phenotypic resistance to tetracycline and ciprofloxacin in the Arrone but not in the Tiber.
In both rivers, diffuse or point pollution sources other than the studied WWTP effluents may account for the observed resistance pattern, although the Arrone appears as more sensitive to the wastewater impact considering its lower flow volume.
污水处理厂（WWTP）是微生物工厂，旨在减少处理后的废水中的营养物和病原微生物的数量，然后再将其排放到环境中。我们研究了城市 WWTP 废水对意大利中部两条河流（Arrone 和 Tiber）最后一段的抗生素耐药基因（ARGs）丰度和抗生素耐药性（AR-）的影响。这两条河流在大小和流量上有所不同。
在三个季节，分别在上游和下游的 WWTP、WWTP 出水口和河口附近的海域采集水样，通过 qPCR 分析 ARGs 的丰度，通过培养和圆盘扩散试验分析 AR-。
尽管收集日期不同，但在所研究的所有基因（、、、、、和）中，Tiber 的绝对浓度在所有采样点均明显高于 Arrone，但两条河流中细菌群落中目标 ARGs 的流行率相似。大多数 ARGs 的绝对浓度也通常在 WWTP 废水中更高，中位数水平在每毫升 4 到 6 个对数拷贝之间，但在研究的河流段上没有差异。在 Arrone 中发现了对四环素和环丙沙星的表型耐药的统计学上显著的地点效应，但在 Tiber 中没有发现。
在这两条河流中，除了研究的 WWTP 废水之外，可能还有其他的弥散或点状污染源导致了所观察到的耐药模式，尽管考虑到 Arrone 的流量较小，它对废水的影响似乎更为敏感。
