摘要

      抗生素耐药基因（ARGs）水平转移介导的耐药性传播，加剧了全球抗生素危机。目前，人们对非抗生素、抗微生物（NAAM）化学品是否与ARGs在环境中的传播有关知之甚少。在这项研究中，我们旨在评估一种普遍存在的NAAM化学物质三氯生（TCS）是否能够促进质粒携带的抗生素耐药基因（ARG）的转化。以携带氨苄西林抗性基因的质粒pUC19为胞外精氨酸，以大肠杆菌DH5α为模型菌，发现在环境检测浓度（0.2μg/L～20μg/L）下，TCS能显著促进质粒载体精氨酸转化大肠杆菌DH5α，转化率可达1.4倍。表型实验、全基因组RNA测序和蛋白质组学分析表明，TCS暴露可刺激活性氧（ROS）产生1.3～1.5倍，诱导细菌膜损伤，上调外膜孔蛋白的翻译。此外，TCS还增强了一般分泌系统Sec（1.4倍）、双精氨酸转位系统Tat（1.2倍）和IV型菌毛分泌系统（2.5倍），可能有助于菌毛对DNA的搜索/捕获。TCS可能通过ROS的过量产生，破坏细胞膜屏障，介导质粒的菌毛捕获和质粒经细胞膜通道的转运，增加ARGs转化大肠杆菌DH5α的频率。本研究表明，在环境相关浓度下，TCS能加速细胞外精氨酸向有活性细菌的转化。这一发现促进了我们对ARGs在生态系统中的命运的理解，并呼吁对NAAM化学品传播抗生素耐药性进行风险评估。

       The dissemination of antibiotic resistance mediated by horizontal transfer of antibiotic resistance genes (ARGs) is exacerbating the global antibiotic crisis. Currently, little is known about whether non-antibiotic, anti-microbial (NAAM) chemicals are associated with the dissemination of ARGs in the environment. In this study, we aimed to evaluate whether a ubiquitous NAAM chemical, triclosan (TCS), is able to promote the transformation of plasmid-borne antibiotic resistance genes (ARGs). By using the plasmid pUC19 carrying ampicillin resistance genes as the extracellular ARG and a model microorganism Escherichia coli DH5ɑ as the recipient, we found that TCS at environmentally detected concentrations (0.2 μg/L to 20 μg/L) significantly enhanced the transformation of plasmid-borne ARGs into E. coli DH5ɑ for up to 1.4-fold. The combination of phenotypic experiments, genome-wide RNA sequencing and proteomic analyses revealed that TCS exposure stimulated the reactive oxygen species (ROS) production for 1.3- to 1.5-fold, induced bacterial membrane damage and up-regulated the translation of outer membrane porin. Moreover, general secretion system Sec (1.4-fold), twin arginine translocation system Tat (1.2-fold) and type IV pilus secretion systems (2.5-fold) were enhanced by TCS, which might contribute to the DNA searching/capture by pilus. Together, TCS might increase the transformation frequency of ARGs into E. coli DH5ɑ by ROS over-production, damaging cell membrane barrier, mediating the pilus capture of plasmid and the translocation of plasmid via cell membrane channels. This study reports that TCS could accelerate the transformation of extracellular ARGs to competent bacteria at environmentally relevant concentrations. The findings advance our understanding of the fate of ARGs in ecosystems and call for risk assessments of NAAM chemicals on disseminating antibiotic resistance.

       https://linkinghub.elsevier.com/retrieve/pii/S0048-9697(20)30131-5