摘要

       抗生素抗性基因 (ARG) 的传播对人类健康和粮食安全构成了全球威胁。因此，对 ARG 库和持久性的评估对于设计和评估减轻 ARG 传播的策略至关重要。本研究开发了一种新的内标方法从水和沉积物中提取细胞外 DNA (eDNA) 和细胞内 DNA (iDNA)，并将其应用于确定中国海河流域中 ARGs 的分配抗生素的使用。沉积物样品中 eDNA 的浓度高于 iDNA，这可能是由于 eDNA 与粘土颗粒和有机物相关联时增强了持久性。 sul1、sul2、tetW 和 tetT 抗生素抗性基因在沉积物中的浓度显着高于水中，并且在沉积物中作为 eDNA 的浓度高于作为 iDNA 的浓度。 ARGs（通常位于质粒 DNA 上）被检测到超过 20 周，染色体编码的 16S rRNA 基因在 8 周后检测不到，表明质粒携带的 ARGs 在河流沉积物中的持久性更高。还观察到添加了细胞外 ARG（即卡那霉素抗性基因）的本土细菌的转化。因此，这项研究表明沉积物中的细胞外 DNA 是一个主要的 ARG 库，可以促进抗生素耐药性的传播。

       The propagation of antibiotic resistance genes (ARGs) represents a global threat to both human health and food security. Assessment of ARG reservoirs and persistence is therefore critical for devising and evaluating strategies to mitigate ARG propagation. This study developed a novel, internal standard method to extract extracellular DNA (eDNA) and intracellular DNA (iDNA) from water and sediments, and applied it to determine the partitioning of ARGs in the Haihe River basin in China, which drains an area of intensive antibiotic use. The concentration of eDNA was higher than iDNA in sediment samples, likely due to the enhanced persistence of eDNA when associated with clay particles and organic matter. Concentrations of sul1, sul2, tetW, and tetT antibiotic resistance genes were significantly higher in sediment than in water, and were present at higher concentrations as eDNA than as iDNA in sediment. Whereas ARGs (frequently located on plasmid DNA) were detected for over 20 weeks, chromosomally encoded 16S rRNA genes were undetectable after 8 weeks, suggesting higher persistence of plasmid-borne ARGs in river sediment. Transformation of indigenous bacteria with added extracellular ARG (i.e., kanamycin resistance genes) was also observed. Therefore, this study shows that extracellular DNA in sediment is a major ARG reservoir that could facilitate antibiotic resistance propagation.

https://pubs.acs.org/doi/abs/10.1021/es404280v