摘要
      质粒在抗微生物耐药性基因（ARGs）的传播中发挥着关键作用，然而，目前对猪生产中源自质粒的ARGs缺乏系统的了解。本文应用定量聚合酶链式反应测定了中国四川、湖北和河北省44个养殖场猪粪中10个ARGs和质粒源的1类整合子基因intI1的患病率。在质粒DNA样品中观察到所有测定的ARGs，并且10个对数拷贝/克的aac（6’）-Ib-cr、blaNDM、blaCTX-M、optrA、ermB、floR、mcr-1、qnrS、tetM、sul1和intI1的平均绝对丰度分别为7.09、2.90、4.67、6.62、7.55、7.14、4.08、4.85、7.16、7.11和8.07。IntI1与猪粪中aac（6’）-Ib-cr和sul1的丰度呈高度相关（r＞0.8，P＜0.01）。此外，农场规模（即牛群数量）和地理位置并不是影响养猪场质粒DNA ARGs绝对丰度的关键因素。然而，氟苯尼考、铜、锌、铁、总磷（TP）和总钾（TK）的浓度与几种ARG的丰度显著相关。特别是Cu和Zn分别与optrA和blaCTX-M具有高度相关性。我们的研究结果表明，抗生素、重金属和环境营养素可能共同导致ARGs在猪生产中的长期持续存在。本研究深入了解了猪粪中ARGs的丰度及其影响因素，对评估和降低畜牧生产中的公共卫生风险具有重要意义。
Abstract
Plasmids play a critical role in the dissemination of antimicrobial resistance genes (ARGs), however, a systematical understanding of ARGs originated from plasmids in swine production is currently lacking. Herein, quantitative polymerase chain reaction was applied to determine the prevalence of ten ARGs and the class1 integron gene intI1 of plasmid source in swine manure from 44 farms in Sichuan, Hubei and Hebei provinces, China. All assayed ARGs were observed in plasmid DNA samples, and the average absolute abundance of aac(6’)-Ib-cr, blaNDM, blaCTX-M, optrA, ermB, floR, mcr-1, qnrS, tetM, sul1 and intI1 were 7.09, 2.90, 4.67, 6.62, 7.55, 7.14, 4.08, 4.85, 7.16, 7.11 and 8.07 of 10 log copies/gram, respectively. IntI1 showed a high correlation (r > 0.8, P < 0.01) with the abundance of aac(6’)-Ib-cr and sul1 in swine manure. Moreover, the farm scale (i.e., herd population) and geographical location were not found to be critical factors influencing the absolute abundance of ARGs of plasmid DNA in swine farms. However, the concentrations of florfenicol, Cu, Zn, Fe, total phosphorus (TP) and total potassium (TK) demonstrated a significant correlation with the abundance of several ARGs. Particularly, Cu and Zn had high correlations with optrA and blaCTX-M, respectively. Our results demonstrated that antibiotics, heavy metals and environmental nutrients are likely jointly contributing to the long-term persistence of ARGs in swine production. This study provides insights into the abundance and influencing factors of ARGs from swine manure, which is of significance for assessing and reducing the public health risks in livestock production.

https://www.sciencedirect.com/science/article/abs/pii/S1001074221005064