Aims Catheter-associated urinary tract infections (CAUTI) caused by Proteus mirabilis are very difficult to treat due to the ability of biofilm formation and drug resistance of these bacteria. The aim of this study was to assess the antibiofilm activity of phages and develop phage cocktail to combat biofilm of P. mirabilis strains. Methods and ResultsConclusionsPlanktonic forms and biofilms of 50 tested uropathogenic P. mirabilis strains showed different sensitivity to 13 phages used. Phages 39APmC32, 65APm2833 and 72APm5211 presenting strong antibiofilm activity were selected as cocktail components. The antibiofilm activity of phage cocktails was similar or slightly higher than that of the most active phage. A three-phage cocktail inhibited biofilm formation and destroyed biofilms of the same number of strains or 2-3 strains more compared to a single phage. The components of the three-phage cocktail did not block each other's activity. The potential of developed anti-P. mirabilis phage cocktail as an antibiofilm agent was proved. Significance and Impact of the StudyIn this study, three broad host range phages presenting strong anti-P. mirabilis biofilm activity were selected. Additionally, high stability of these viruses makes them a useful tool for controlling the biofilms.