Efficacy of low irradiance violet-blue light for the inactivation of attached and biofilm-associated bacteria on clinically-relevant materials

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Sinclair, Lucy G. and Anderson, John G. and MacGregor, Scott J. and MacLean, Michelle (2026) Efficacy of low irradiance violet-blue light for the inactivation of attached and biofilm-associated bacteria on clinically-relevant materials. Proceedings of SPIE: The International Society for Optical Engineering, 13829. 138290F. ISSN 1996-756X (https://doi.org/10.1117/12.3090096)

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Abstract

Frequently-touched surfaces within patient care areas represent a primary reservoir for healthcare-associated infection transmission. Violet-blue 405nm light, which is antimicrobial at levels safe for human exposure, has shown successful application for continuous environmental decontamination within clinical spaces. This study demonstrates the efficacy of low irradiance 405nm light, at levels of ∼0.5mW/cm2, which is representative of that used in environmental systems, for inactivation of attached and biofilm-associated bacteria on clinically-relevant inert surfaces. Staphylococcus aureus was seeded onto a range of surface materials (polyvinyl chloride, stainless steel, glass and vinyl) and exposed to 0.5mW/cm2 405nm light for 4h (∼7J/cm2) and 24h (∼43J/cm2). To evaluate the impact of 405nm light exposure in biofilms, monolayer and mature biofilms were also prepared on the same materials, with light exposure (0.5mW/cm2; 4h to 24h) conducted either during biofilm development or post-formation to evaluate efficacy for inhibition of biofilm formation, and inactivation of established biofilms, respectively. Successful reductions of surface-seeded bacteria were demonstrated (1.66 to 2.03 log10 CFU/coupon; 97.0 to 98.9% inactivation). Further, on all surfaces, biofilm formation was inhibited by 2.75 to 4.57 log10 CFU/coupon, and successful reductions of monolayer and mature biofilms was demonstrated (0.92 to 1.71 log10 CFU/coupon; 66.6-96.7% inactivation and 0.47 to 2.41 log10 CFU/coupon; 61.2 to 99.4% inactivation, respectively). Overall, this study demonstrates the susceptibility of both surface-seeded and biofilm-associated bacteria on inert surfaces to low irradiance 405nm light, supporting its use as a method for environmental decontamination within clinical spaces, with potential to substantially reduce and prevent spread of healthcare-associated infections.

ORCID iDs

Sinclair, Lucy G. ORCID logoORCID: https://orcid.org/0009-0007-8121-7795, Anderson, John G. ORCID logoORCID: https://orcid.org/0000-0003-4151-1619, MacGregor, Scott J. ORCID logoORCID: https://orcid.org/0000-0002-8810-1716 and MacLean, Michelle ORCID logoORCID: https://orcid.org/0000-0001-5750-0397;
CORE (COnnecting REpositories)