摘要

       限制动物饲养操作可以促进与抗生素耐药性相关的基因的传播。目前尚不清楚从肉牛背景操作中移除牛如何影响环境中抗生素抗性基因 (ARG) 的持久性。我们研究了停止肉牛背景操作对肉牛背景环境中 ARG 的持久性和分布的影响。该研究是在牧场饲养场类型的肉牛背景操作中进行的，该操作由带入口门的围栏分隔的喂食区和放牧区组成。在将牛从设施中移除之前，背景已经进行了七年。在牛被移走之前的基线处收集了来自 26 个地理参考位置的土壤样本 (n = 78)，然后在牛被移走一年和两年后收集。从土壤样品和总细菌种群 (16S rRNA)、肠球菌总数和 1 类整合子 (intI1)、红霉素 (ermB 和 ermF)、磺胺 (sul1 和 sul2) 和四环素 (tetO、tetW 和 tetQ) 中提取宏基因组 DNA ) 抗性基因被量化。总细菌、肠球菌属、1 类整合子和 ARG 在饲养区及其附近（围栏和大门周围）的浓度较高，随后沿放牧区呈梯度下降。尽管在牛移出两年后饲养区总细菌、肠球菌属、1 类整合子和 ARGs 的浓度显着下降，但它们的浓度仍然高于放牧区观察到的浓度。与放牧区相比，饲养区两年内更高的浓度表明，受限肉牛生产系统对土壤中细菌和 ARG 的持久性具有持久影响。

       Confined animal feeding operations can facilitate the spread of genes associated with antibiotic resistance. It is not known how cattle removal from beef cattle backgrounding operation affects the persistence of antibiotic resistance genes (ARGs) in the environment. We investigated the effect of cessation of beef cattle backgrounding operation on the persistence and distribution of ARGs in the beef cattle backgrounding environment. The study was conducted at a pasture-feedlot type beef cattle backgrounding operation which consisted of feeding and grazing areas that were separated by a fence with an access gate. Backgrounding occurred for seven years before cattle were removed from the facility. Soil samples (n = 78) from 26 georeferenced locations were collected at the baseline before cattle were removed, and then one year and two years after cattle were removed. Metagenomic DNA was extracted from the soil samples and total bacterial population (16S rRNA), total Enterococcus species and class 1 integrons (intI1), and erythromycin (ermB and ermF), sulfonamide (sul1 and sul2) and tetracycline (tetO, tetW and tetQ) resistance genes were quantified. Concentrations of total bacteria, Enterococcus spp., class 1 integrons, and ARGs were higher in the feeding area and its immediate vicinity (around the fence and the gate) followed by a gradient decline along the grazing area. Although the concentrations of total bacteria, Enterococcus spp., class 1 integrons and ARGs in the feeding area significantly decreased two years after cattle removal, their concentrations were still higher than that observed in the grazing area. Higher concentrations over two years in the feeding area when compared to the grazing area suggest a lasting effect of confined beef cattle production system on the persistence of bacteria and ARGs in the soil.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212510