Building-level wastewater surveillance of antimicrobial resistance in the general, student and hospital-associated populations

Antimicrobial resistance (AMR) patterns were investigated in three wastewater catchments in Perugia, Central Italy: an urban wastewater treatment plant influent, a university building, and a large hospital, used as proxies for the general, student, and hospital-associated populations, respectively. Monthly samples were collected from February to July 2025 and analysed using culture-based methods for third-generation cephalosporin resistant Escherichia coli (3GCR- Ec ) and vancomycin-resistant enterococci (VRE), together with qPCR/dPCR quantification of selected antimicrobial resistance genes and intI1 . 3GCR- Ec prevalence was comparable across the three populations, suggesting a broadly shared community-associated resistance background. In contrast, VRE showed a clear gradient, with the highest levels in hospital wastewater, intermediate values in urban wastewater, and the lowest levels in university wastewater. Molecular analyses identified a group of abundant markers consistently detected across populations ( intI1 , sul1 , ermB and tetA ) and a more variable group ( qnrS , bla CTX-M , bla KPC and vanA ) that better discriminated population-specific AMR profiles, particularly the hospital-associated one. These findings support the value of wastewater surveillance at different spatial resolutions for identifying AMR patterns associated with distinct population settings and expected antimicrobial pressures.