摘要

       在动物饲养操作（AFOs）中，抗生素被用于控制、预防和治疗疾病。抗生素处理过的家畜粪便中含有未经代谢的抗生素，对细菌产生选择性压力，促进抗微生物耐药性（AMR）的表达。行间作物施用有机肥是种植者为满足作物养分需要而采用的一种农艺措施，但同时也是土壤和水环境中AMR的来源。本研究旨在直接比较爱荷华州中部两个相邻（221至229公顷）施肥集水区和非施肥集水区（肥料比较）和三个受肥料影响的集水区（600至804公顷）、未知肥料施用（控制）和城市影响（混合土地利用比较）的出口径流AMR指标。监测的AMR指标包括抗生素耐药基因（ARGs）、ermB、ermF（大环内酯）、tetA、tetM、tetO、tetW（四环素）、sul1、sul2（磺胺）、aadA2（氨基糖苷）、vgaA和vgaB（胸膜多糖）、泰乐菌素和四环素耐药肠球菌。肥料比较结果显示，2017年施用肥料的集水区四环素和泰乐菌素抗性细菌明显较高（p<0.05），但2018年没有差异，可能是由于兽医饲料指令导致抗生素使用发生变化。此外，精氨酸分析表明，在肥料改良的集水区，精氨酸的多样性更大。混合土地利用比较表明，与城市影响区相比，肥料改良区2017年四环素耐药菌显著高于城市影响区（p<0.05），2017年和2018年泰乐菌素耐药菌显著高于城市影响区。受城市影响的集水区在两个采样年的ermB浓度均显著高于对照组，但施用有机肥的集水区径流中总arg相对丰度较高。此外，两个集水区的AMR指标均高于对照集水区。本研究确定了四种农业源（tetM、tetW、sul1、sul2）可能是AMR特有的arg，并优化用于流域尺度监测研究以跟踪环境中的抗性。

         Antibiotics are administered to livestock in animal feeding operations (AFOs) for the control, prevention, and treatment of disease. Manure from antibiotic treated livestock contains unmetabolized antibiotics that provide selective pressure on bacteria, facilitating the expression of anti-microbial resistance (AMR). Manure application on row crops is an agronomic practice used by growers to meet crop nutrient needs; however, it can be a source of AMR to the soil and water environment. This study in central Iowa aims to directly compare AMR indicators in outlet runoff from two adjacent (221 to 229 ha) manured and non-manured catchments (manure comparison), and among three catchments (600 to 804 ha) with manure influence, no known manure application (control), and urban influences (mixed land use comparison). Monitored AMR indicators included antibiotic resistance genes (ARGs) ermB, ermF (macrolide), tetA, tetM, tetO, tetW (tetracycline), sul1, sul2 (sulfonamide), aadA2 (aminoglycoside), vgaA, and vgaB (pleuromutilin), and tylosin and tetracycline resistant enterococci bacteria. Results of the manure comparison showed significantly higher (p<0.05) tetracycline and tylosin resistant bacteria from the catchment with manure application in 2017, but no differences in 2018, possibly due to changes in antibiotic use resulting from the Veterinary Feed Directive. Moreover, the ARG analysis indicated a larger diversity of ARGs at the manure amended catchment. The mixed land use comparison showed the manure amended catchment had significantly higher (p<0.05) tetracycline resistant bacteria in 2017 and significantly higher tylosin resistant bacteria in 2017 and 2018 than the urban influenced catchment. The urban influenced catchment had significantly higher ermB concentrations in both sampling years, however the manure applied catchment runoff consisted of higher relative abundance of total ARGs. Additionally, both catchments showed higher AMR indicators compared to the control catchment. This study identifies four ARGs that might be specific to AMR as a result of agricultural sources (tetM, tetW, sul1, sul2) and optimal for use in watershed scale monitoring studies for tracking resistance in the environment.

         https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6953785/