Cadena Marlynn, Durso Lisa M, Miller Daniel N, Waldrip Heidi M, Castleberry B L, Drijber Rhae A, Wortmann Charles
Department of Biological Sciences, College of Science, The University of Texas at El Paso, El Paso, TX, United States.
Agroecosystem Management Research Unit, Agricultural Research Service, United States Department of Agriculture, Lincoln, NE, United States.
Front Microbiol. 2018 Jun 28;9:1283. doi: 10.3389/fmicb.2018.01283. eCollection 2018.
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 ( = 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 (Q) (49%), (S) (46%), (X) (30%), and (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 (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 12 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.
人们普遍认为应降低农业抗生素耐药性，然而，从现有文献中尚不清楚合适的降低目标是什么。有机农场提供了一个独特的机会，可将农业抗生素使用问题与土壤中的抗生素耐药性问题区分开来。在本研究中，从内布拉斯加州的12个认证有机农场采集土壤，评估四环素和磺胺类耐药基因的存在情况（共15个目标），并与土壤物理、化学和生物学参数进行关联分析。在所有12个农场的土壤中以及196个土壤样本中的182个（93%）中发现了四环素和磺胺类抗生素耐药基因（ARGs）。最常检测到的基因是tetG（占样本的55%），其次是（Q）（49%）、（S）（46%）、（X）（30%）和（P）（29%）。土壤从两个深度采集。未观察到基于土壤深度的ARGs差异。注意到ARGs的存在与土壤电导率以及钙、钠和Mehlich-3磷的浓度之间存在正相关。本研究的数据表明，选定的土壤特性与个别四环素耐药基因之间可能存在关系，包括（O），它是环境样本的常见目标。我们将有机农场的结果与先前发表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常被检测到。有趣的是，当按基因机制对四环素ARG结果进行分类时，外排基因在草原土壤中的频率通常更高，而核糖体保护和酶基因在有机农场土壤中更常被检测到，这表明特定四环素耐药机制可能具有生态作用。通过将有机农场的土壤与草原土壤进行比较，我们可以开始确定低化学投入农业生产实践对多种耐药性指标的基线影响。
