Quorum sensing inhibition: A novel mechanism for ferrate-mediated removal of antibiotic resistance genes in swine wastewater.

The widespread occurrence of antibiotic resistance genes (ARGs) in the environment poses a severe threat to public health, with swine wastewater (SW) being a significant reservoir. Current technologies show limited efficacy in ARGs removal. This study evaluated the efficacy, long-term durability, and safety of ferrate (Fe(Ⅵ)) in removing clinically important ARGs (i.e., cfr, optrA, poxtA, efrA) from SW. The removal of ARGs were quantified via qPCR. The underlying mechanisms were systematically investigated through measurements of reactive oxygen species (ROS), antioxidant responses, membrane permeability, extracellular DNA (eDNA), biofilm formation (BF), Autoinducer-2 (AI-2) activity, and its synthase gene (pfs) abundance, with validations using ROS scavenger, exogenous AI-2 addition, and a cfr-positive E. coli pure culture. Water quality parameters and acute toxicity (using Vibrio fischeri) were measured for the treated samples to assess the potential environmental risk. Results indicated that Fe(Ⅵ) (40-160 mg/L) exhibited concentration-dependent removal of the ARGs without rebound within 30d post-treatment or acute toxicity, with 160 mg/L being optimal. This may be achieved through the synergy of direct oxidation and oxidative stress (OS), which concurrently caused (1) host neutralization: halting ARGs replication and dissemination through bacterial inactivation; (2) eDNA release: promoting the release of ARGs-carrying eDNA via cell membrane damage and lysis, thereby increasing the possibility of ARGs exposure and degradation; and (3) quorum sensing inhibition (QSI): disrupting BF by decreasing AI-2 activity and pfs abundance, which may prevent the environmental accumulation of ARGs and suppress their horizontal transfer. AI-2-mediated quorum sensing was identified as a novel strategic target for ARGs control in SW.