Methylene Blue–mediated Antimicrobial Photodynamic Therapy for Antibiotic-Resistant Cystitis: Experimental Rationale and Clinical Prospects

This narrative review examines the rationale for methylene blue–mediated antimicrobial photodynamic ther­apy (aPDT) in antibiotic-resistant bacterial cystitis. Photochemical mechanisms, susceptibility of planktonic uropatho­gens and biofilms, experimental bladder infection models, and translational limitations are discussed. In vitro studies report inactivation of antibiotic-resistant Escherichia coli, although biofilms require different exposure conditions. In a rat urinary tract infection model, methylene blue combined with potassium iodide shortened infection duration, but recurrence was observed. Clinical evidence supporting intravesical aPDT for cystitis remains insufficient. Standardized assessment of microbiological efficacy, urothelial integrity, and safety is essential before routine clinical use.