Antimicrobial Efficacy of Tea Tree Oil Against Pseudomonas aeruginosa in Contact Lenses

PURPOSE: To evaluate the antibacterial and antibiofilm activity of tea tree oil (TTO) against a multidrug-resistant (MDR) Pseudomonas aeruginosa isolate, used as a representative model of the primary pathogen associated with contact lens-related keratitis. METHOD: TTO was tested for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill kinetics against P. aeruginosa . Biofilm (BF) formation and eradication assays were conducted using crystal violet (CV) and MTT viability tests on biofilms grown on CL surfaces. Cytotoxicity was evaluated in vitro using murine cone photoreceptor cells (661W). RESULTS: TTO showed strong antibacterial activity against MDR P. aeruginosa , with MIC and MBC values of 3.5 and 7 mg/mL, respectively. It inhibited biofilm formation and eradicated mature biofilms on silicone hydrogel contact lenses, outperforming commercial multipurpose solutions ( P <0.05). Cytotoxicity assays in 661W cells revealed a narrow therapeutic window, as effective concentrations were close to cytotoxic levels. CONCLUSIONS: TTO shows strong antibacterial and antibiofilm activity against MDR P. aeruginosa , outperforming commercial solutions in biofilm reduction. Although the narrow margin between effective and cytotoxic concentrations limits direct ocular use, its incorporation into contact lens care solutions appears promising for safe and effective prevention of microbial keratitis.