摘要

       对抗生素生产废水的研究表明，在水环境中，即使是单一的抗生素也能筛选出多药耐药菌。在高浓度抗生素作用下，质粒可能是多药耐药的重要机制。本文以从可培养微生物群落中提取的质粒DNA为载体，在添加0（对照）或25mg/L土霉素（OTC-25）的生物废水处理反应器中构建了两个亚基因组文库。OTC-25纤溶酶体被分为72个抗生素耐药基因（ARGs），它们对13种抗生素产生了耐药性。在25 mg/L土霉素浓度下，质粒中富集了编码四环素、氨基糖苷、磺胺和多药耐药基因的显性ARGs。此外，在OTC-25纤溶酶原中发现17个连续的多精氨酸携带者contigs（携带≥2个精氨酸），而对照组仅发现9个。将OTC-25质粒的读谱与完全测序的质粒进行比对，发现携带多药耐药转运体（pecM）、四环素耐药基因（tetA、tetR）和转座酶基因的豚鼠气单胞菌IncU耐药质粒pFBAOT6可能是OTC-25质粒中一个潜在的流行耐药质粒。另外，两个新的耐药质粒（包含携带多药耐药操纵子mexCD-oprJ的contig C301682和携带tet36和转座酶基因的contig C301632）也可能是OTC-25质粒库中潜在的流行耐药质粒。这项研究将有助于更好地了解质粒在高浓度抗生素水环境中MDR形成中的作用。

       Studies on antibiotic production wastewater have shown that even a single antibiotic can select for multidrug resistant bacteria in aquatic environments. It is speculated that plasmids are an important mechanism of multidrug resistance (MDR) under high concentrations of antibiotics. Herein, two metagenomic libraries were constructed with plasmid DNA extracted from cultivable microbial communities in a biological wastewater treatment reactor supplemented with 0 (CONTROL) or 25 mg/L of oxytetracycline (OTC-25). The OTC-25 plasmidome reads were assigned to 72 antibiotic resistance genes (ARGs) conferring resistance to 13 types of antibiotics. Dominant ARGs, encoding resistance to tetracycline, aminoglycoside, sulfonamide, and multidrug resistance genes, were enriched in the plasmidome under 25 mg/L of oxytetracycline. Furthermore, 17 contiguous multiple-ARG carrying contigs (carrying ≥ 2 ARGs) were discovered in the OTC-25 plasmidome, whereas only nine were found in the CONTROL. Mapping of the OTC-25 plasmidome reads to completely sequenced plasmids revealed that the conjugative IncU resistance plasmid pFBAOT6 of Aeromonas caviae, carrying multidrug resistance transporter (pecM), tetracycline resistance genes (tetA, tetR), and transposase genes, might be a potential prevalent resistant plasmid in the OTC-25 plasmidome. Additionally, two novel resistant plasmids (containing contig C301682 carrying multidrug resistant operon mexCD-oprJ and contig C301632 carrying the tet36 and transposases genes) might also be potential prevalent resistant plasmids in the OTC-25 plasmidome. This study will be helpful to better understand the role of plasmids in the development of MDR in water environments under high antibiotic concentrations.