Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA, USA.
National Laboratory for Agriculture and the Environment, USDA-ARS, Ames, IA, USA.
Sci Total Environ. 2018 Jan 1;610-611:1173-1179. doi: 10.1016/j.scitotenv.2017.08.116. Epub 2017 Aug 30.
The Midwestern United States is dominated by agricultural production with high concentrations of swine, leading to application of swine manure onto lands with artificial subsurface drainage. Previous reports have indicated elevated levels of antibiotic resistance genes (ARGs) in surface water and groundwater around confined animal feeding operations which administer antimicrobials. While previous studies have examined the occurrence of ARGs around confined swine feeding operations, little information is known how their transport from tile-drained fields receiving swine manure application impacts downstream environments. To further our knowledge in this area, water samples were collected from five locations in the agriculturally dominated South Fork Iowa River Watershed with approximately 840,000 swine present in the 76,000ha basin. Samples were collected monthly from three stream sites and two main artificial subsurface drainage outlets. Samples were analyzed for macrolide resistance genes ermB, ermF and 16S rRNAgene abundance using qPCR. Abundance of erm genes ranged from below limits of quantification to >10 copies 100mL water. Eighty-nine percent of stream water samples contained one of these two ARGs. Results indicate significantly more ermB and ermF in main drainage outlets than stream samples when normalized by 16S rRNA abundance (p<0.0001). Both artificial drainage locations revealed temporal trends for ermB and ermF abundance when normalized to 16S rRNA abundance. The higher resistance gene concentrations identified in artificial drainage samples occurring mid-Spring and late-Fall are likely due to manure application.
美国中西部地区以农业生产为主，生猪养殖高度集中，导致大量猪粪施用于具有人工地下排水系统的土地上。先前的报告表明，在使用抗生素的集约化养殖设施周围的地表水和地下水中，抗生素抗性基因（ARGs）的水平升高。虽然先前的研究已经检查了集约化养猪场周围 ARGs 的出现情况，但对于从接受猪粪施用的有瓦楞排水系统的田地中转移的 ARGs 如何影响下游环境，人们知之甚少。为了进一步了解这方面的知识，从农业为主的爱荷华河支流流域的五个地点采集了水样，该流域约有 84 万头猪，流域面积为 76000 公顷。每月从三个溪流地点和两个主要的人工地下排水口采集水样。使用 qPCR 分析了水样中的大环内酯类抗性基因 ermB、ermF 和 16S rRNA 基因丰度。erm 基因的丰度从低于定量下限到 >10 个拷贝 100mL 水不等。89%的溪流水样含有这两个 ARGs 中的一个。结果表明，当与 16S rRNA 丰度归一化时，主排水口的 ermB 和 ermF 明显多于溪流样本（p<0.0001）。当与 16S rRNA 丰度归一化时，两个人工排水地点都显示出 ermB 和 ermF 丰度的时间趋势。在春中和秋末发现的人工排水样本中，抗性基因浓度较高，可能是由于粪肥的施用。
