Efficacy of photoClO2 against two human norovirus surrogates and Clostridioides difficile endospores on stainless steel and nylon carpet.

Aims Determine efficacy of an aqueous photocatalytic disinfection system, photoClO₂, against two human norovirus surrogates [feline calicivirus (FCV) and Tulane virus (TuV)] and Clostridioides difficile endospores on stainless steel and nylon carpet. Methods and results The photoClO₂ system was first optimized with 1% sodium chlorite (NaClO₂) and 10 ppm Eosin Y to produce 60.64 ppm ClO₂/min in a 4.5 × 4.5 cm² area. It was then tested against FCV, TuV, and C. difficile endospores on stainless steel and nylon carpet with two different backings. On stainless steel, photoClO₂ achieved a > 5 log₁₀ plaque-forming unit (PFU) reduction of FCV in 45 min, >3 log₁₀ median tissue culture infectious dose (TCID₅₀) reduction of TuV in 60 min, and 1.3 log₁₀ colony-forming unit (CFU) reduction of C. difficile endospores in 120 min. Under indoor lighting conditions, photoClO₂ achieved a 4.3 log₁₀ PFU reduction of FCV and 1.4 log₁₀ TCID₅₀ reduction of TuV on stainless steel after 120 min. Further, photoClO₂ achieved a 2.9 log₁₀ PFU reduction of FCV and 2.5 log₁₀ TCID₅₀ reduction of TuV on nylon carpet with waterproof backing in 60 min, which was higher than carpet with water-permeable backing (1.3 log₁₀ PFU and 1.1 log₁₀ TCID₅₀ reduction, respectively). Conclusion ClO₂ production rate of the photoClO₂ system was influenced by light distribution, while disinfection efficacy was affected by light intensity, surface characteristics, and target microorganisms. PhotoClO₂ was efficacious in inactivating both human norovirus surrogates on stainless steel and nylon carpet. Efficacy against C. difficile endospores was limited. [ABSTRACT FROM AUTHOR]