Universal decontamination of hospital surfaces in an occupied inpatient room with a continuous 405 nm light source.
S E Bache, M Maclean, G Gettinby, J G Anderson, S J MacGregor, I Taggart
Author Information
S E Bache: Burns Unit, Canniesburn Plastic Surgery Unit, Glasgow Royal Infirmary, Glasgow, UK. Electronic address: sarahbache@doctors.org.uk.
M Maclean: The Robertson Trust Laboratory for Electronic Sterilisation Technologies (ROLEST), Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK; Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK.
G Gettinby: Department of Mathematics and Statistics, University of Strathclyde, Glasgow, UK.
J G Anderson: The Robertson Trust Laboratory for Electronic Sterilisation Technologies (ROLEST), Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK.
S J MacGregor: The Robertson Trust Laboratory for Electronic Sterilisation Technologies (ROLEST), Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK.
I Taggart: Burns Unit, Canniesburn Plastic Surgery Unit, Glasgow Royal Infirmary, Glasgow, UK.
BACKGROUND: Previous work has shown that a ceiling-mounted, 405 nm high-intensity narrow-spectrum light environmental decontamination system (HINS-light EDS) reduces bacterial contamination of environmental surfaces in a burns unit by between 27% and 75%. Examination of the efficacy of the light over extended exposure times and its probable mode of action was performed. AIM: To ascertain the correlation between bacterial kill achieved on sampled surface sites around the burns unit and both irradiance levels of the 405 nm light, and exposure time. METHODS: Seventy samples were taken using contact agar plates from surfaces within an occupied side-room in the burns unit before, during, and after a seven-day use of the HINS-light EDS. This was repeated in three separate studies. Statistical analysis determined whether there was significant decrease in environmental contamination during prolonged periods of HINS-light treatment, and whether there was an association between irradiance and bacterial kill. FINDINGS: A decrease of between 22% and 86% in the mean number of surface bacteria was shown during the use of the HINS-light EDS. When the light ceased to be used, increases of between 78% and 309% occurred. There was no correlation between bacterial kill and irradiance levels at each sampling site but strong correlation between bacterial kill and exposure time. CONCLUSION: Prolonged exposure to the HINS-light EDS causes a cumulative decontamination of the surfaces within a burns unit. The importance of exposure time and possible airborne effect over irradiance levels is emphasized.
