| Summary: | As a consequence of global demographic challenges, both the artificial and the natural environment are increasingly impacted by contaminants of emerging concern, such as bacterial pathogens and their antibiotic resistance genes (ARGs). The aim of this study was to determine the extent to which anthropogenic contamination contributes to the spread of antibiotic resistant enterococci in aquatic compartments and to explore genetic relationships among <i>Enterococcus</i> strains. Antimicrobial susceptibility testing (ampicillin, imipenem, norfloxacin, gentamycin, vancomycin, erythromycin, tetracycline, trimethoprim-sulfamethoxazole) of 574 isolates showed different rates of phenotypic resistance in bacteria from wastewaters (91.9–94.4%), hospital effluents (73.9%), surface waters (8.2–55.3%) and groundwater (35.1–59.1%). The level of multidrug resistance reached 44.6% in enterococci from hospital effluents. In all samples, except for hospital sewage, the predominant species were <i>E. faecium</i> and <i>E. faecalis</i>. In addition, <i>E. avium</i>, <i>E. durans</i>, <i>E. gallinarum</i>, <i>E. aquimarinus</i> and <i>E. casseliflavus</i> were identified. <i>Enterococcus faecium</i> strains carried the greatest variety of ARGs (<i>bla</i><sub>TEM-1</sub>, <i>aac(6′)-Ie-aph(2″)</i>, <i>aac(6′)-Im</i>, <i>vanA</i>, <i>vanB, ermB</i>, <i>mefA</i>, <i>tetB</i>, <i>tetC</i>, <i>tetL</i>, <i>tetM</i>, <i>sul1</i>), while <i>E. avium</i> displayed the highest ARG frequency. Molecular typing using the ERIC2 primer revealed substantial genetic heterogeneity, but also clusters of enterococci from different aquatic compartments. Enterococcal migration under anthropogenic pressure leads to the dispersion of clinically relevant strains into the natural environment and water resources. In conclusion, ERIC-PCR fingerprinting in conjunction with ARG profiling is a useful tool for the molecular typing of clinical and environmental <i>Enterococcus</i> species. These results underline the need of safeguarding water quality as a strategy to limit the expansion and progression of the impending antibiotic-resistance crisis.
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