Dissemination of antimicrobial resistance in surface waters: surveillance of enterococci and coliform bacteria in Slovakia.

Antimicrobial-resistant faecal bacteria represent an increasing environmental concern in surface waters impacted by anthropogenic activities. Surveillance of enterococci and coliform bacteria, particularly Escherichia coli, is widely used to assess the dissemination of antimicrobial resistance in aquatic environments. These ecosystems may act as reservoirs of resistance determinants, where subinhibitory antibiotic concentrations promote their persistence and horizontal transfer, posing a potential public health risk.This study aimed to survey antibiotic‑resistant coliform bacteria and enterococci in surface waters and associated sediments in the southern part of central Slovakia. Total coliforms were detected in all analysed water and sediment samples. E. coli was present in 50% of water samples and 75% of sediment samples, with sediments generally containing higher concentrations of both total coliforms and E. coli. Resistant coliform isolates predominantly exhibited multidrug resistance and strong biofilm‑forming capacity. Genes encoding broad‑spectrum β‑lactamases were detected in most isolates, with blaTEM being the most prevalent. In isolates with reduced carbapenem susceptibility, blaNDM was detected. Enterococci were detected in 63% of water samples and 75% of sediment samples, including En. faecalis, En. faecium, and En. durans. High resistance to ampicillin and vancomycin was observed, and three isolates carried the vanA resistance gene.These findings highlight the role of surface waters in disseminating antimicrobial resistance in Slovakia and underscore the importance of continued surveillance in aquatic ecosystems.