Antimicrobial Resistance in the Ganga River Ecosystem: Linking Heavy Metal Pollution, Microbial Communities, and Environmental Resistance

Antimicrobial resistance (AMR) has emerged as a major global public health and environmental challenge, with freshwater ecosystems increasingly recognized as important reservoirs and dissemination pathways for antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and metal resistance genes (MRGs). Among these ecosystems, the Ganga River represents a unique and globally significant model for investigating the interactions between microbial ecology, environmental pollution, heavy metal contamination, and resistance evolution. The river receives substantial inputs of municipal sewage, industrial effluents, hospital wastewater, agricultural runoff, pharmaceutical residues, and emerging contaminants, creating strong selective pressures that influence microbial community structure and function. This review synthesizes current knowledge regarding riverine microbial communities, the occurrence and dissemination of ARB and ARGs, heavy metal pollution, microbial metal tolerance mechanisms, and the role of co-selection in maintaining environmental resistomes, with particular emphasis on the Ganga River. Recent metagenomic and resistome-based investigations have revealed widespread distributions of ARGs, MRGs, virulence factors, and mobile genetic elements (MGEs) throughout both water and sediment environments. Sediments frequently harbor higher microbial diversity and greater abundances of resistance determinants than overlying waters, highlighting their importance as long-term environmental reservoirs. Particular attention is given to the mechanisms linking heavy metal contamination and antimicrobial resistance, including cross-resistance, co-resistance, and co-regulation pathways that facilitate the persistence and dissemination of resistance determinants. The review further discusses environmental and public health implications associated with resistance dissemination, including human exposure pathways, emergence of multidrug-resistant pathogens, and One Health concerns. Modern approaches for resistance monitoring, including metagenomics, shotgun sequencing, resistome analysis, bioinformatics, and GIS-based surveillance, are evaluated. Finally, key mitigation strategies, including wastewater treatment improvements, industrial discharge management, environmental surveillance, and policy interventions approaches, are highlighted. Further, the evidence demonstrates that the Ganga River functions as a significant environmental reservoir of antimicrobial resistance and underscores the urgent need for integrated One Health strategies to mitigate resistance dissemination and protect ecosystem and public health.