This study explores reusable benzyldimethyldodecyl ammonium chloride (BDMDAC) immobilised on hydroxyapatite microparticles as a contact-restricted post-treatment for wastewater. These functionalised particles achieved up to ~5.5 log bacterial reduction and removed clinically relevant antibiotic resistance genes (ARGs) in treated effluents, with efficacy retained after multiple reuses and no detectable leaching. Importantly, the approach suppressed horizontal gene transfer, showed no enrichment of QAC or other ARGs, and worked independently of plasmid-borne resistance backgrounds.
By confining antimicrobial action to the particle interface, it avoids sub-inhibitory gradients that typically drive resistance selection in soluble disinfectants. This offers a promising, evolution-conscious strategy for mitigating ARB/ARG release from treatment plants into the environment, with implications for industrial hygiene, water reuse, and sustainable cleaning formulations.
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