摘要

      内布拉斯加州有机耕作土壤中的四环素和磺胺类抗生素抗性基因。人们普遍认为应降低农业抗生素抗性，然而，从现有文献中尚不清楚什么是合适的降低目标。有机农场提供了一个独特的机会，将农业抗生素药物使用问题与土壤中的抗生素耐药性问题分开。在这项研究中，从内布拉斯加州12个经认证的有机农场采集土壤，评估是否存在四环素和磺胺类抗药性基因（n=15个靶点），并与土壤物理、化学和生物参数相关。12个农场土壤中均发现四环素和磺胺类抗生素耐药基因（ARGs），196份土壤样品中有182份（93%）。最常见的检测基因是tetG（55%的样本），其次是tet（Q）（49%）、tet（S）（46%）、tet（X）（30%）和tetA（P）（29%）。从两个深处采集土壤。根据土壤深度，没有观察到ARGs的差异。ARG的存在与土壤电导率、Ca、Na和Mehlich-3磷浓度呈正相关。本研究的数据指出了土壤特性与四环素抗性基因之间可能存在的关系，包括tet（O），tet（O）是环境样本的共同目标。我们将有机农场的结果与以前公布的草原土壤数据进行了比较，发现12个基因的检测频率存在显著差异，其中8个基因在草原土壤中更为常见。值得注意的是，当四环素ARG结果按基因机制分类时，流出基因在草原土壤中的频率普遍较高，而核糖体保护和酶基因在有机农田土壤中的检测频率较高，这表明四环素抗性机制可能具有生态作用。通过比较有机农场土壤和草原土壤，我们可以开始确定低化学投入农业生产实践对多种抗性措施的基线效应。

      There is widespread agreement that agricultural antibiotic resistance should be reduced, however, it is unclear from the available literature what an appropriate target for reduction would be. Organic farms provide a unique opportunity to disentangle questions of agricultural antibiotic drug use from questions of antibiotic resistance in the soil. In this study, soil was collected from 12 certified organic farms in Nebraska, evaluated for the presence of tetracycline and sulfonamide resistance genes (n = 15 targets), and correlated to soil physical, chemical, and biological parameters. Tetracycline and sulfonamide antibiotic resistance genes (ARGs) were found in soils from all 12 farms, and 182 of the 196 soil samples (93%). The most frequently detected gene was tetG (55% of samples), followed by tet(Q) (49%), tet(S) (46%), tet(X) (30%), and tetA(P) (29%). Soil was collected from two depths. No differences in ARGs were observed based on soil depth. Positive correlations were noted between ARG presence and soil electrical conductivity, and concentrations of Ca, Na, and Mehlich-3 phosphorus. Data from this study point to possible relationships between selected soil properties and individual tetracycline resistance genes, including tet(O) which is a common target for environmental samples. We compared organic farm results to previously published data from prairie soils and found significant differences in detection frequency for 1

2 genes, eight of which were more commonly detected in prairie soils. Of interest, when tetracycline ARG results were sorted by gene mechanism, the efflux genes were generally present in higher frequency in the prairie soils, while the ribosomal protection and enzymatic genes were more frequently detected in organic farm soils, suggesting a possible ecological role for specific tetracycline resistance mechanisms. By comparing soil from organic farms with prairie soils, we can start to determine baseline effects of low-chemical input agricultural production practices on multiple measures of resistance.

       https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033193/