Hospital Effluent Discharges as Dynamic Hotspots for Multidrug-resistant Pathogens: Sources, Selection, Dissemination, Surveillance and Control

Abstract

Hospital effluent is widely described as a hotspot for antimicrobial resistance, yet the term hotspot is often used without distinguishing concentration, absolute load, clinical relevance, mobility, selection pressure, temporal variability or downstream exposure. This critical narrative review evaluates hospital wastewater as a dynamic ecological and infrastructural interface linking healthcare, sewerage systems, treatment processes and receiving environments. Literature published from 2000 to 1 June 2026 was identified through accessible scholarly indexes, institutional sources and citation searching, with foundational earlier work retained where necessary. The evidence consistently shows that hospital discharges can contain clinically important multidrug-resistant bacteria, antibiotic resistance genes, mobile genetic elements, antimicrobial residues, disinfectants and other co-selective agents. The strongest evidence concerns enrichment of carbapenem-resistant and extended-spectrum beta-lactamase-producing Gram-negative bacteria, localised selection under antibiotic exposure, and incomplete removal during wastewater treatment. Nevertheless, the magnitude and persistence of a hospital-specific signal vary substantially with hospital type, patient mix, prescribing practices, hydraulic dilution, sewer travel, treatment configuration, season and analytical method. Community wastewater may exceed hospital discharges in total antimicrobial-resistance load because of its much larger volume, while DNA-based detection alone cannot establish viability, pathogenicity, transfer or infection risk. Conventional and advanced treatments generally reduce bacterial and genetic loads, but performance is process-specific and may be obscured by relative-abundance metrics, extracellular DNA, regrowth and survivor selection. The review proposes that hotspot status should be judged through an integrated framework combining hazard intensity, clinically relevant host-gene linkage, evolutionary opportunity, temporal dynamics and exposure connectivity. Risk-tiered source control, better hospital stewardship, longitudinal flow-weighted surveillance, host-resolved genomics and outcome-linked intervention studies are more defensible than universal assumptions about on-site treatment. Hospital effluent is therefore an important but context-dependent control point within a wider One Health antimicrobial-resistance system.