Tracking Antimicrobial Resistance in Environmental Waters: Risks, Routes, and Regulatory Needs

Background: Antimicrobial resistance (AMR) in gram-negative bacteria represents a growing global health threat, increasingly fueled by environmental factors. Wastewater, agricultural runoff, aquaculture, and pharmaceutical discharge contribute to the release of antibiotic residues, resistant bacteria, and resistance genes into ecosystems. Objective: This literature review explores the environmental persistence and dissemination of antibiotic resistance, focusing on the mechanisms by which multidrug-resistant (MDR) genes are maintained and transferred—particularly through water sources—and highlights emerging mitigation strategies and regulatory challenges. Key Findings: Gram-negative bacteria such as Salmonella enterica and ESKAPE pathogens exhibit intrinsic and acquired resistance mechanisms, including efflux pumps and mobile genetic elements. Environmental reservoirs, especially wastewater treatment plants, facilitate horizontal gene transfer between pathogenic and non-pathogenic bacteria. Agricultural practices, antibiotic overuse, and inadequate waste management further exacerbate the spread. While ozone treatment, membrane bioreactor systems, bacteriophage therapy, and efflux pump inhibitors show promise in reducing AMR load, widespread implementation remains limited. Policy efforts—at federal, state, and international levels—lack consistency and enforcement, particularly regarding environmental discharge and regulation of antibiotic residues. Conclusion: Environmental AMR, particularly via water systems, poses a substantial public health risk. A coordinated One Health approach, incorporating policy reform, technological advancements, and cross-sector collaboration, is essential to address AMR at its environmental source and mitigate its global spread.