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

A study in Perugia, Italy examined antimicrobial resistance (AMR) patterns in wastewater from three distinct sources: an urban treatment plant, a university building, and a large hospital. These samples represented the general, student, and hospital-associated populations, respectively. Monthly samples were collected from February through July 2025 and examined using both culture-based methods and quantitative PCR techniques to detect specific resistance markers.

The prevalence of third-generation cephalosporin resistant Escherichia coli (3GCR-Ec) was similar across all three populations, indicating a shared community-associated resistance background. However, vancomycin-resistant enterococci (VRE) showed a distinct gradient, with the highest levels in hospital wastewater, intermediate levels in urban wastewater, and the lowest levels in university wastewater.

Molecular analyses revealed two groups of resistance markers: a consistent group (intI1, sul1, ermB, and tetA) found across all populations, and a more variable group (qnrS, blaCTX-M, blaKPC, and vanA) that helped differentiate the population-specific AMR profiles, particularly highlighting the unique hospital-associated profiles.

These findings underscore the utility of wastewater surveillance at varying spatial scales for identifying AMR patterns linked to unique population settings and anticipated antimicrobial exposures. This research was funded by Regione Umbria as part of Italy's National Action Plan for Combating Antimicrobial Resistance (PNCAR 2022-2025).