Effects of Triclosan on the Development of Antimicrobial Resistance in the Environment: A Review

Purpose of Review Triclosan (TCS), a widely used broad-spectrum antimicrobial agent, enters to wastewater treatment plants (WWTPs) and the environment ultimately after its usage. Notably, the use of TCS has surged during the outbreak of COVID-19, leading to the environment under increasing TCS pollution pressure. Even environmentally relevant concentrations of TCS can promote the development of antimicrobial resistance (AMR), which is a major public health concern. The purpose of this study is to provide a basis for the management and risk assessment of TCS by providing a holistic review of the impact of TCS on AMR in the environment. Recent Findings Bacterial resistance to TCS mainly takes place through modification or replacement of the FabI enzyme, which is the main target of TCS in bacteria. Currently, multiple FabI mutants and isoenzymes have been identified in the environment giving bacterial resistance to TCS. In addition, mechanisms by which TCS promotes bacterial development of resistance to other antimicrobials have been studied in laboratory experiments and environmental settings, such as anaerobic digester. TCS will promote the development of AMR in the environment with the possibility of adverse risks to public health. Summary This review systematically summarizes the mechanisms of bacterial resistance to antimicrobials driven by TCS and highlights the effects of TCS in promoting the horizontal transfer and enrichment of antibiotic resistance genes (ARGs). Suggestions for overcoming the limitations of laboratory-scale studies and further improving the risk assessment of TCS in the environment are proposed.