Work

Sodium hypochlorite residual in the environment facilitated the spread of antibiotic resistance genes: through microplastics as a medium

Year: 2026

Type: article

Abstract: • Residual NaClO in WWTPs loses its ability to remove ARGs. • ARGs relative abundance were further increased under NaClO stress with MPs co-exposure. • Compared to MPs alone, ARGs abundance are further increased by NaClO residual. • Selective enrichment level of ARB/ARGs on MPs-biofilm are promoted by NaClO residual. • Surface morphology of MPs is changed by NaClO residual. • VGT and HGT of ARGs are facilitated by MPs and NaClO co-exposure. Most pollutants in the environment exist in complex forms, and exploring the impact of a single pollutant lacks wide applicability. The co-exposure of microplastics (MPs) and NaClO in wastewater treatment plants (WWTPs) is a widespread occurrence. At present, relevant reports on the impact of individual NaClO or MPs on antibiotic resistance genes (ARGs) have been established. Herein, this study investigated the fate of antibiotic-resistant bacteria (ARB) and ARGs after exposure to MPs with or without NaClO stress. In this study, the total ARG abundance increased by 11.83% under MPs stress, and further increases by 17.89% under NaClO stress with MPs co-exposure. The mechanism was that the presence of NaClO promoted the selective enrichment of potential ARB and ARGs on the MPs-biofilm. The surface morphology of the MPs was changed and the attached biofilm became thicker, which provided a suitable environment for the proliferation of ARB and the spread of ARGs. Vertical gene transfer (VGT) and horizontal gene transfer (HGT) of ARGs were facilitated by MPs under NaClO stress. Specifically, the VGT of ARGs was facilitated via enhanced bacterial cell proliferation (by 132.66%), and relevant functional genes are also increased. HGT of ARGs is promoted by the increasing relative abundance of mobile genetic elements (MGEs). ARG-carrying plasmids are also demonstrated that MPs promoted HGT of ARGs in the presence of NaClO. The increase in oxidative stress, cell membrane permeability, and Type IV secretion system (T4SS) collaboration facilitated the HGT of ARGs. In summary, co-exposure to NaClO and MPs promote VGT and HGT of ARGs through the variation in MPs structure and the enhancement of MPs-biofilms. Furthermore, the presence of MPs restrained the disinfection effect of NaClO, with an inhibition rate higher than 50%.

Source: Environment International

DOI: 10.1016/j.envint.2026.110048

Authors: Jin Xu, Xiuhong Liu, Shiyong Zhang, Jiaxin Li, Qing Yang

Institutions: Chinese Academy of Sciences, Beijing University of Technology, Research Center for Eco-Environmental Sciences, National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology

Language: English

Topic: Pharmaceutical and Antibiotic Environmental Impacts

Subfield: Pollution

Field: Environmental Science

Domain: Physical Sciences

SDGs: Clean water and sanitation, Good health and well-being, Responsible consumption and production

Open Access status: gold

Estimated APC paid: $4,750