The bacterial infection that involves antimicrobial resistance is a rising global threat to public health. Chlorine-based water disinfection processes can inactivate antibiotic resistant bacteria. However, at the same time, these processes may cause the release of antibiotic resistance genes into the water as free DNA, and consequently increase the risk to disseminate antibiotic resistance via natural transformation. Presently, little is known about the contribution of residual chlorine affecting the transformation of extracellular antibiotic resistance genes (ARGs). This study investigates whether chloramine and free chlorine promote the transformation of ARGs and how this may occur. We reveal that both chloramine and free chlorine, at practically relevant concentrations, significantly stimulated the transformation of plasmid-encoded ARGs by the recipient Acinetobacter baylyi ADP1, by up to a 10-fold increase. The underlying mechanisms underpinning the increased transformations were revealed. Disinfectant exposure induced a series of cell responses, including increased levels of reactive oxygen species (ROS), bacterial membrane damage, ROS-mediated DNA damage, and increased stress response. These effects thus culminated in the enhanced transformation of ARGs. This promoted transformation was observed when exposing disinfectant-pretreated A. baylyi to free plasmid. In contrast, after pretreating free plasmid with disinfectants, the transformation of ARGs decreased due to the damage of plasmid integrity. These findings provide important insight on the roles of disinfectants affecting the horizontal transfer of ARGs, which could be crucial in the management of antibiotic resistance in our water systems.

涉及抗菌素耐药性的细菌感染是对公共卫生的日益严重的全球威胁。氯基水消毒工艺可以使抗生素耐药细菌失活。然而，与此同时，这些过程可能导致抗生素抗性基因以游离 DNA 的形式释放到水中，从而增加通过自然转化传播抗生素抗性的风险。目前，关于余氯影响细胞外抗生素抗性基因（ARGs）转化的作用知之甚少。本研究调查了氯胺和游离氯是否会促进 ARG 的转化，以及这种转化是如何发生的。我们发现氯胺和游离氯在实际相关浓度下，Acinetobacter baylyi ADP1，增加了 10 倍。揭示了支持增加的转换的潜在机制。消毒剂暴露引起一系列细胞反应，包括活性氧 (ROS) 水平升高、细菌膜损伤、ROS 介导的 DNA 损伤和应激反应增加。因此，这些影响最终导致 ARG 的转化增强。当暴露经过消毒剂预处理的A. baylyi时观察到这种促进的转化释放质粒。相反，用消毒剂预处理游离质粒后，由于质粒完整性受损，ARGs 的转化率降低。这些发现为消毒剂影响 ARG 水平转移的作用提供了重要见解，这对于我们水系统中抗生素耐药性的管理可能至关重要。