Lakes and lagoons used for drinking water supply and fisheries as sources of potentially pathogenic bacteria and antimicrobial resistance

: Drinking water supplies and water basins used for fisheries represent two essential water sources for humans. Despite the growing accessibility of metagenomic approaches, their routine use for water quality monitoring is still limited. Many key water resources have yet to be fully characterized in terms of microbiome, pathobiome, and antimicrobial resistome. In this study, surface water samples were collected over one year from the artificial Lake Bidighinzu (drinking water supply) and the coastal lagoon Cabras (fisheries) located in the western Mediterranean area. Samples were analyzed for physical and chemical properties, and 16S rRNA gene amplicon and shotgun sequencing were used to characterize bacterial communities, pathobiomes, and antimicrobial resistomes. Physical and chemical properties were generally similar between sites, except for higher salinity in Cabras Lagoon. In Cabras Lagoon, richness of the bacterial community and pathobiome was generally higher in the largest trophic fraction (>20 μm), while in both sites the abundance of potentially pathogenic bacteria (PPB) increased at this fraction. PPB, including ESKAPE pathogens, were more abundant in Lake Bidighinzu. The overall antimicrobial resistome was similar across sites, with high-risk antimicrobial resistance genes (ARGs) such as emrB prevalent. Lake Bidighinzu also had more contigs where ARGs co-occurred with mobile genetic elements. This study highlights microbiological risks in two aquatic systems, particularly Lake Bidighinzu, and underscores the need to integrate metagenomic approaches, possibly with cultivation-based methods, to monitor water quality and assess health risks in drinking water supplies and fisheries.