Validation of a Thymol-Based Disinfectant for Surface Decontamination: Standardized Carrier Testing and Real-Use Performance Assessment

Environmental surfaces are important reservoirs for microbial contamination and play an important role in pathogen transmission in healthcare, pharmaceutical, and controlled environments.The present study investigated the surface antimicrobial activity of a thymol-based disinfectant formulation (0.2% w/w) by using a combination of standardized quantitative carrier testing and real-use assessment.Surface antimicrobial activity was assessed on seven non-porous materials (stainless steel, polyvinyl chloride, glass, polymethyl methacrylate, epoxy resin, vinyl paint and silicone) by means of carrier tests compliant with EN 13697 using six reference microorganisms representing bacteria, yeasts and filamentous fungi.To assess the in situ efficacy of the products, they were applied directly (spray-and-wipe protocol) onto doors, walls and floors inside a controlled environment.Microbial contamination was quantified by contact plate sampling before and after disinfection.The thymol-based formulation achieved log10 reductions well above the acceptance criteria for EN 13697 (≥5 for bacteria, ≥4 for fungi/yeasts) on all tested materials, with bacterial reductions ranging from 6.29 to 6.82 log10 and fungal reductions from 4.98 to 5.46 log10.In situ application was significant for surface decontamination, with microbial counts reduced to near-zero levels on high-touch surfaces (doors: 0 CFU/plate; walls: 0-6 CFU/plate; floors: 0-12 CFU/plate) although baseline contamination levels were frequently above detection limits.The correlation between standard laboratory results and performance in real use confirms the predictive value of EN 13697 testing for this formulation.These results indicate that the thymol-based formulation constitutes a validated and safe alternative to conventional chemical disinfectants, with possible additional benefits in material compatibility, environmental sustainability, and occupational safety.