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

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

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.

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.

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.

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