摘要

本研究对海河沉积物样品中5类抗生素抗性基因( ARGs )进行了定量分析，其丰度范围为1.39×104～1.58×1010拷贝/ g干重。同时，通过筛选交配试验从这些样品中分离出抗生素抗性接合质粒。共分离到202种转导接合子，并对其抗生素抗性表型进行测试，其中观察到26种不同类型的接合质粒。这些质粒大多具有多重抗性表型，最常见的抗性为四环素抗性和磺胺抗性。此外，我们还检测了这些质粒的转移频率，确定了它们的基因型，并将质粒携带的ARGs与海河地区相应的丰度进行了比较。大多数分离的质粒表现出对受体菌株大肠杆菌J53的高转移频率。从海河市区分离的质粒转移频率高于农村地区。综合分析质粒基因型、ARG丰度和质粒测序结果，证实海河流域质粒携带的ARG多为显性基因。因此，从海河分离到的接合质粒对ARGs在海河中的分布、丰度和空间分布起着至关重要的作用，特别是一些不常见的ARGs如blaGES - 1。本研究将有助于提高对环境中结合质粒介导的ARG传播的认识。

In this study, five classes of antibiotic resistance genes (ARGs) were quantified in sediment samples of Haihe River, China, with abundance ranging from 1.39 × 104to 1.58 × 1010 copies/g dry weight. Meanwhile, antibiotic resistant conjugative plasmids were also isolated from these samples through filter mating assays. In total, 202 transconjugants were isolated and tested for their antibiotic resistance phenotypes, among which 26 different types of conjugative plasmids were observed. The majority of these plasmids showed a multi-resistant phenotype and the most prevalent resistance was tetracycline resistance and sulfonamide resistance. Furthermore, we tested the transfer frequencies of these plasmids, determined their genotypes and then compared the plasmid-borne ARGs with their corresponding abundance in Haihe River. Most of the isolated plasmids exhibited high transfer frequencies to the recipient strain Escherichia coli J53. Plasmids isolated from the urban areas of Haihe River have higher transfer frequencies than the rural areas. Results from comprehensive analysis of plasmid genotypes, ARG abundance and plasmid sequencing confirmed that most of the plasmid-borne ARGs were the dominant genes in the Haihe River. Therefore, conjugative plasmids isolated from the Haihe River plays a crucial role in the dissemination, abundance and spatial distribution of ARGs in Haihe River, especially some unfrequent ARGs like blaGES-1. This study will help to increase the knowledge on the conjugative plasmid-mediated ARG propagation in the environment.

https://www.sciencedirect.com/science/article/pii/S0043135416309903