EC Microbiology

The effect of manual cleaning and disinfection depend on how careful it is done, and the technique used. Disinfection with H₂O₂, acidic acid or ozon products are all based on chemicals with toxic effects. Ultraviolet light C is a chemical free disinfection method which do not demand sealing of the room before the disinfection and ventilation after disinfection. The aim of this study was to test the effect of a new disinfection system for room disinfection using UVC light.

For laboratory test eight different strains of well-known clinical isolates of test bacteria were used and placed on a laminated wood plate and exposed to UVC light up to 90 minutes. For field test, imprints were taken from five spots before and after exposure to UVC light in an outpatient clinic.

Gram negative bacteria were reduced about 8 log₁₀ at 3m and 6 log₁₀ at 5m. Gram positive bacteria were less susceptible to UVC light the reduction was around 6 log₁₀ at 3m and around 5 log₁₀ at 5m. Vancomycin resistant Enterococcus faecium seem to be less sensitive to UVC than other Gram-positive bacteria. The bacteria distribution on each spot in the field test were the same before and after UVC but the number of bacteria was clearly reduced during the disinfection. Chairs were the most contaminated spots.

In conclusion, UVC light is an effective method, to kill bacteria in the laboratory, but also very effective to disinfect patients’ rooms in short time.

Keywords: Ultraviolet Light; UVC; Room Disinfection; C. difficile; VRE; A. baumannii; S. aureus; Laboratory Test; Field Test

1. Boyce JM. “Environmental contamination makes an important contribution to hospital infections”. Journal of Hospital Infection2 (2007): 504.
2. Otter JA., et al. “The role played by contaminated surfaces in the transmission of nosocomial pathogens”. Infection Control and Hospital Epidemiology7 (2011): 687-699.
3. Bergen LK., et al. “Spread of bacteria on surfaces when cleaning with microfiber cloths”. Journal of Hospital Infection2 (2009): 132-137.
4. Blazejewski C., et al. “Efficiency of hydrogen peroxide in improving disinfection of ICU rooms”. Critical Care 19 (2015): 30.
5. Fu TY., et al. “Efficacy, efficiency and safety aspects of hydrogen peroxide vapor and aerosolized hydrogen peroxide room disinfection systems”. Journal of Hospital Infection3 (2012): 199-205.
6. Weber DJ., et al. “Effectiveness of ultraviolet devices and hydrogen peroxide systems for terminal room decontamination: Focus on clinical trials”. American Journal of Infection Control5 (2016): e77-e84.
7. Hawley B., et al. “Respiratory Symptoms in Hospital Cleaning Staff Exposed to a Product Containing Hydrogen Peroxide, Peracetic Acid, and Acetic Acid”. Annals of Work Exposures and Health1 (2017): 28-40.
8. Batakliev T., et al. “Ozone decomposition”. Interdisciplinary Toxicology2 (2014): 47-59.
9. Kapdan A., et al. “Comparing the antibacterial activity of gaseous ozone and chlorhexidine solution on a tooth cavity model”. Journal of Clinical and Experimental Dentistry3 (2013): e133-e137.
10. Sadraeian M., et al. “Viral inactivation by light”. ELight1 (2022): 18.
11. Health Quality Ontario. “Portable Ultraviolet Light Surface-Disinfecting Devices for Prevention of Hospital-Acquired Infections: A Health Technology Assessment”. Ontario Health Technology Assessment Series1 (2018): 1-73.
12. Thornton GM., et al. “The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: A systematic review of ultraviolet radiation”. PLoS One4 (2022): e0266487.
13. Norval M., et al. “The effects of ultraviolet light irradiation on viral infections”. British Journal of Dermatology6 (1994): 693-700.
14. Lanteri MC., et al. “Inactivation of a broad spectrum of viruses and parasites by photochemical treatment of plasma and platelets using amotosalen and ultraviolet A light”. Transfusion6 (2020): 1319-1331.
15. Clancy JL., et al. “Susceptibility of five strains of Cryptosporidium parvum oocysts to UV light”. American Water Works Association3 (2004): 84-93.