摘要
      对抗生素生长促进剂的限制促使牲畜生产商使用替代生长促进剂，目前在生猪生产中广泛使用膳食铜补充剂。然而，高剂量的膳食铜构成了抗生素耐药性共同选择的风险，并且风险可能取决于所使用的铜基饲料添加剂的类型。我们在这里报道了第一个对照实验，研究了两种对比的铜基饲料添加剂对整个猪肠微生物组和抗生素耐药性的影响。从116天内四个时间点采集的120头猪的粪便样本（n=96）中提取DNA，这些样本被分配给三种饮食处理：对照、二价硫酸铜（CuSO4；250μg Cu g−1饲料）和单价氧化铜（Cu2O；250μgCu g−2饲料）。评估了细菌群落组成、抗生素抗性基因（ARGs）和可移动遗传元件（MGE），并使用全细胞细菌生物反应器测定了生物可利用Cu（[Cu]bio）。饲料中添加铜可使粪便中的总铜浓度（[Cu]总量）和[Cu]生物量分别增加8-10倍和至少670-1000倍，但两种铜源之间没有显著差异。在整个实验过程中，无论采用何种治疗方法，猪肠道微生物组都含有丰富多样的ARG和MGE。微生物组在猪的生长阶段之间存在显著差异，并随着时间的推移趋于收敛，但只有细菌群落组成和耐药性的微小变化可能与补充铜有关。Procrustes分析发现，细菌群落组成（即存在的细菌分类群）与ARG流行模式之间存在显著相关性。总的来说，实验结果并没有为铜诱导的ARGs或MGE的共同选择提供证据，即使铜浓度水平超过了欧盟猪日粮的最大允许水平（25至150μg铜g−1饲料，取决于猪的年龄）。
Abstract
Restrictions on antibiotic growth promoters have prompted livestock producers to use alternative growth promoters, and dietary copper (Cu) supplementation is currently being widely used in pig production. However, elevated doses of dietary Cu constitute a risk for co-selection of antibiotic resistance and the risk may depend on the type of Cu-based feed additives being used. We here report the first controlled experiment investigating the impact of two contrasting Cu-based feed additives on the overall swine gut microbiome and antibiotic resistome. DNA was extracted from fecal samples (n = 96) collected at four time points during 116 days from 120 pigs allotted to three dietary treatments: control, divalent copper sulfate (CuSO4; 250 μg Cu g−1 feed), and monovalent copper oxide (Cu2O; 250 μg Cu g−1 feed). Bacterial community composition, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) were assessed, and bioavailable Cu ([Cu]bio) was determined using whole-cell bacterial bioreporters. Cu supplementation to feed increased total Cu concentrations ([Cu]total) and [Cu]bio in feces 8–10 fold and at least 670–1000 fold, respectively, but with no significant differences between the two Cu sources. The swine gut microbiome harbored highly abundant and diverse ARGs and MGEs irrespective of the treatments throughout the experiment. Microbiomes differed significantly between pig growth stages and tended to converge over time, but only minor changes in the bacterial community composition and resistome could be linked to Cu supplementation. A significant correlation between bacterial community composition (i.e., bacterial taxa present) and ARG prevalence patterns were observed by Procrustes analysis. Overall, results of the experiment did not provide evidence for Cu-induced co-selection of ARGs or MGEs even at a Cu concentration level exceeding the maximal permitted level for pig diets in the EU (25 to 150 μg Cu g−1 feed depending on pig age).

https://www.sciencedirect.com/science/article/pii/S0048969722067092