Probiotics as a Promising Alternative: Evaluating Commercial Strains Against Urinary Tract Infection Pathogens

Background The increasing prevalence of antibiotic-resistant uropathogens has compromised the effectiveness of conventional therapies for urinary tract infections (UTIs), necessitating alternative or adjunct antimicrobial strategies. Objectives This study aimed to evaluate the in vitro antimicrobial activity of commercially available probiotic formulations against clinically isolated uropathogens and to assess their potential synergistic interactions with conventional antibiotics. Methods A total of 350 urine samples were collected and identified through cultural, microscopic, and biochemical analyses. Antibiotic susceptibility was determined by disc diffusion method. Four commercially available probiotics (Acteria, Proteria, Prokult, and Prolacto) were evaluated for antagonistic activity using agar well diffusion, drop-test, and overlay methods. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined via broth microdilution. Synergistic activity between probiotics and selected antibiotics was assessed by incorporating probiotics into antibiotic discs. Result Escherichia coli , Proteus mirabilis , and Serratia marcescens were identified as predominant uropathogens and exhibited high resistance to tested antibiotics. All probiotic formulations exhibited significant antagonistic activity in drop-test and overlay assays, producing inhibition zones of 21–31 mm, whereas no activity was detected using agar well diffusion. MIC values ranged from 21–341 mg/mL, with MBC values up to 682 mg/mL, indicating pathogen-dependent susceptibility. Notably, probiotic–antibiotic combinations significantly enhanced antibacterial efficacy. Piperacillin (100 μg), which showed minimal activity alone (2–3 mm), increased to 17 mm when combined with Prokult against P. mirabilis . Ciprofloxacin inhibition zones expanded from 24–30 mm to 36–38 mm, and Gentamicin activity against S. marcescens increased from 12 mm to 20 mm. Conclusion Commercially available probiotics exhibit potent antagonistic activity and significant synergy with conventional antibiotics against resistant uropathogens. These findings suggest that probiotic–antibiotic combinations may represent a promising adjunctive strategy to mitigate AMR and improve UTI treatment.