Research objectives: To determine the mechanism of the antimicrobial and anti adhesion effect of nitroxoline (5-nitro-8-hydroxyquinoline) on uropathogenic enterococci. To examine the interaction between nitroxoline with hydroquinone or gentamicin and their effect on the prevention of biofilm formation as well as on the treatment of urinary infections caused by Enterococcus. Methods: In our research, 29 clinical isolates of uropathogenic E. faecalis strains and the standard ATCC 29212 strain were used. Clinical isolates were characterized by various biochemical methods, 16S rRNA sequencing, protein profile (MALDI-TOF) and the ability to form biofilm. Antimicrobial efficiency was tested by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum antiadhesion concentration (MAC). The protein profile of enterococci before and after treatment was examined using MALDI-TOF MS analysis, while the morphological changes of bacterial cells after treatment were monitored by transmission electron microscopy (TEM), and changes in the biofilm structure using scanning electron microscopy (SEM). Results: The tested uropathogenic enterococci show a similar biochemical and protein profile and differ by ability to form biofilm as well as sensitivity to selected antimicrobial agents. Nitroxoline exhibits bacteriostatic and anti-adhesion effects on uropathogenic enterococci, which is further enhanced when combined with hydroquinone or gentamicin. Most combinations of hydroquinone and nitroxoline aswell as gentamicin and nitroxoline show an additive effect on all strains of enterococci. Conclusion: The mentioned combinations could become a potential therapeutic solution for the treatment of urinary infections caused by enterococci, but it is necessary to further investigate the mechanisms of action