The study identified various antimicrobial resistance genes (ARGs) in the Iskar River downstream of a wastewater treatment plant (WWTP), including genes conferring resistance to macrolides, tetracyclines, beta-lactams, sulfonamides, and carbapenems. Notably, the carbapenemase genes bla OXA-58 and bla IMP-33-like were detected, which are typically associated with clinical settings.