Study of the Impact of Antibiotic Combinations Used in Urinary Tract Infections on the Effectiveness of Antimicrobial Therapy

Background: Biofilm-associated urinary tract infections (UTIs) pose a significant therapeutic challenge due to the increased tolerance of biofilm-embedded bacteria to antimicrobial agents and the high risk of infection recurrence. The increasing prevalence of multidrug-resistant uropathogens necessitates the evaluation of alternative therapeutic strategies, including antibiotic combination therapy. This study aimed to assess the antibiofilm activity of selected antibiotics used individually and in combination against biofilms formed by clinically relevant uropathogens. Methods: Biofilms of Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, and Enterococcus faecalis isolated from patients with UTIs were developed on polystyrene microtiter plates and exposed to ciprofloxacin, nitrofurantoin, amikacin, and imipenem applied as monotherapy and in combinations. Biofilm biomass reduction was quantified spectrophotometrically using crystal violet staining and expressed as a percentage relative to untreated controls. Results: Antibiotic monotherapy produced moderate reductions in biofilm biomass, with efficacy dependent on bacterial species and antibiotic concentration. In contrast, antibiotic combinations demonstrated enhanced antibiofilm activity. The ciprofloxacin–nitrofurantoin combination showed increased biofilm biomass reduction compared with monotherapy against P. aeruginosa and E. coli. The imipenem–amikacin combination reduced P. mirabilis biofilm biomass by over 80%. Conclusions: These findings suggest that rationally selected antibiotic combinations may represent a more effective strategy than monotherapy for controlling biofilm-associated UTIs.