Efficacy of Violet-Blue (405 nm) LED Lamps for Disinfection of High-Environmental-Contact Surfaces in Healthcare Facilities: Leading to the Inactivation of Microorganisms and Reduction of MRSA Contamination

Abstract

Effective disinfection procedures in healthcare facilities are essential to prevent transmission. Chemical disinfectants, hydrogen peroxide vapour (HPV) systems and ultraviolet (UV) light are commonly used methods. An emerging method, violet-blue light at 405 nm, has shown promise for surface disinfection. Its antimicrobial properties are based on producing reactive oxygen species (ROS) that lead to the inactivation of pathogens. Studies have shown significant efficacy in reducing bacterial levels on surfaces and in the air, reducing nosocomial infections. The aim of this study was to evaluate the antimicrobial effectiveness of violet-blue (405 nm) LED lamps on high-contact surfaces in a hospital infection-control laboratory. High-contact surfaces were sampled before and after 7 days of exposure to violet-blue light. In addition, the effect of violet-blue light on MRSA-contaminated surfaces was investigated. Exposure to violet-blue light significantly reduced the number of bacteria, yeasts and moulds on the sampled surfaces. The incubator handle showed a low microbial load and no growth after irradiation. The worktable and sink showed an inconsistent reduction due to shaded areas. In the second experiment, violet-blue light significantly reduced the microbial load of MRSA on surfaces, with a greater reduction on steel surfaces than on plastic surfaces. Violet-blue light at 405 nm has proven to be an effective tool for pathogen inactivation in healthcare settings Violet-blue light shows promise as an additional and integrated tool to reduce microbial contamination in hospital environments but must be used in combination with standard cleaning practices and infection control protocols. Further research is needed to optimise the violet-blue, 405 nm disinfection method.

Keywords: HAI; LED technology; MRSA; UV radiation; disinfection; surface contamination; violet-blue light.

Figure 1

Photoradiometric simulation of the violet-blue light distribution in the laboratory where the tests were carried out. Above is the three-dimensional plane of light distribution, representing intensity with a colorimetric scale associated with irradiance values (in W/m²); below left is the section of the room seen from above with ceiling lights and below right without ceiling lights.

Figure 2

(A) Map of sampling points: areas sampled are outlined in red: (i) desk, (ii) keyboard, (iii) incubator handle, (iv) worktable and (v) sink. (B) Map of lamps positioned on the ceiling: the three lamps were positioned at the same distance from the perimeter walls of the room in order to illuminate all laboratory surfaces as equally as possible.

Figure 3

Work surfaces disinfection, irradiated with violet-blue light. Data are expressed as mean ± SD (standard deviation) of three determinations carried out in adjacent areas at the same point. The number of CFU of bacteria, yeasts and moulds was evaluated as described in the Section 2. Statistical analysis of the raw data was performed by t-test.

Figure 4

Inactivation of MRSA after exposure to the violet-blue lamp. Data are expressed as mean ± SD (n = 3). * p < 0.05 (CFU after irradiation, days 1–3–5–7, vs. CFU before irradiation, day 0).