Decontamination of patient bathroom surfaces with 405 nm violet-blue light irradiation in a real-life setting

Background: Irradiation with violet-blue light (VBL), in the spectrum of 405-450 nm, has been reported to be effective against pathogenic bacteria.

Aim: To investigate whether VBL irradiation could reduce the level of surface contamination at seven shared patient bathrooms in two wards at a hospital in Sweden.

Methods: Repeated sampling of five separate surfaces (door handle, tap water handle, floor, toilet seat, and toilet armrest) was performed in the bathrooms where 405 nm light-emitting diode spotlights had been installed. A prospective study with a cross-over design was carried out, which included two study periods, first with the spotlights either switched on or off and a second study period with the opposite spotlight status.

Findings: In total, 665 surface samples were collected during the study (133 samples per surface). Bacterial growth was found in 84% of all samples. The most common findings were coagulase-negative staphylococci and Bacillus spp. The median number of colony-forming units (cfu)/cm² was 15 (interquartile range: 5-40) for all surfaces. In our main outcome, mean cfu/cm² of all surfaces in a bathroom, no difference was observed with or without VBL. Clean surfaces (<5 cfu/cm²) were more commonly observed in bathrooms with VBL, also when controlling for confounding factors. No difference was observed in the number of heavily contaminated surfaces.

Conclusion: This study did not safely demonstrate an additive effect on bacterial surface levels when adding VBL to routine cleaning in shared patient bathrooms.