School of Environmental Science and Engineering, Tianjin University , Tianjin 300072, China.
Environ Sci Technol. 2014;48(1):71-8. doi: 10.1021/es404280v. Epub 2013 Dec 11.
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.
抗生素耐药基因（ARGs）的传播对人类健康和食品安全构成了全球性威胁。因此，评估 ARG 库和持久性对于制定和评估减轻 ARG 传播的策略至关重要。本研究开发了一种从水和沉积物中提取细胞外 DNA（eDNA）和细胞内 DNA（iDNA）的新型内部标准方法，并应用该方法来确定中国海河盆地 ARGs 的分布情况，该流域抗生素使用强度较大。沉积物样本中的 eDNA 浓度高于 iDNA，这可能是由于 eDNA 与粘土颗粒和有机物结合时具有更高的持久性。磺胺类、四环素类和耐甲氧西林基因在沉积物中的浓度明显高于水中，并且在沉积物中作为 eDNA 的浓度高于作为 iDNA。虽然 ARGs（通常位于质粒 DNA 上）可检测 20 多周，但 8 周后可检测到的染色体编码 16S rRNA 基因不可检测，这表明质粒携带的 ARGs 在河流沉积物中的持久性更高。还观察到添加的细胞外 ARG（即卡那霉素耐药基因）对土著细菌的转化。因此，本研究表明，沉积物中的细胞外 DNA 是一个主要的 ARG 库，可能促进抗生素耐药性的传播。
