Microplastics as Emerging Vectors of Antimicrobial Resistance in Aquatic Environments: Mechanisms, Evidence, and Research Priorities

Abstract

Microplastics have emerged as ubiquitous contaminants of aquatic environments, while antimicrobial resistance has become an increasingly important environmental and public-health concern. Although these problems have traditionally been investigated separately, growing evidence indicates that microplastics can provide surfaces on which microorganisms, antibiotic resistance genes (ARGs), mobile genetic elements, and chemical contaminants interact. This review examines the current evidence concerning the role of microplastics in the environmental emergence, persistence, and dissemination of antimicrobial resistance, with particular attention to aquatic ecosystems and wastewater treatment systems. An integrative literature review was conducted using peer-reviewed studies and authoritative scientific and public-health reports addressing microplastics, antibiotic-resistant bacteria, ARGs, mobile genetic elements, wastewater, and aquatic environments. The reviewed evidence indicates that microplastic surfaces can support distinct microbial communities, promote biofilm formation, concentrate chemical contaminants, and create conditions that may favor horizontal gene transfer and the persistence of resistance determinants. Recent metagenomic evidence further suggests that microplastic-associated microbial communities can contain enriched collections of antibiotic, metal, and biocide resistance genes and mobile genetic elements. Wastewater treatment plants represent an important convergence point because they receive microplastics, antibiotics, resistant bacteria, and ARGs while simultaneously generating effluent and sludge capable of transporting these contaminants into receiving environments. However, important uncertainties remain concerning the extent to which microplastic-associated resistance contributes to clinically relevant infections. The review concludes that microplastics should be considered a potentially important component of environmental antimicrobial-resistance pathways rather than an established independent driver of human disease. Standardized monitoring, mechanistic experiments, metagenomic surveillance, and integrated wastewater management are needed to clarify their contribution and reduce environmental risks.