Inactivation of Bacterial Pathogens following Exposure to Light from a 405-Nanometer Light-Emitting Diode Array

Abstract

This study demonstrates the susceptibility of a variety of medically important bacteria to inactivation by 405-nm light from an array of light-emitting diodes (LEDs), without the application of exogenous photosensitizer molecules. Selected bacterial pathogens, all commonly associated with hospital-acquired infections, were exposed to the 405-nm LED array, and the results show that both gram-positive and gram-negative species were successfully inactivated, with the general trend showing gram-positive species to be more susceptible than gram-negative bacteria. Detailed investigation of the bactericidal effect of the blue-light treatment on Staphylococcus aureus suspensions, for a range of different population densities, demonstrated that 405-nm LED array illumination can cause complete inactivation at high population densities: inactivation levels corresponding to a 9-log 10 reduction were achieved. The results, which show the inactivation of a wide range of medically important bacteria including methicillin-resistant Staphylococcus aureus, demonstrate that, with further development, narrow-spectrum 405-nm visible-light illumination from an LED source has the potential to provide a novel decontamination method with a wide range of potential applications.

A Possible Mechanism for the Bactericidal Effect of Visible Light

“…aureus -MRSA, S. epidermidis, S. pyogenes, C. perfringens; Gram-negative bacteria: A. baumannii, P. aeruginosa, E. coli, P. vulgaris and K. pneumoniae. 7) Wavelengths of longer than 430nm were found to induce no effect on the viability of S. aureus cells. These results are in contrast to those of Chukuka 8) and Guffey 9) who found a significant killing effect of S. aureus at 470nm.…”

405 nm light exposure of osteoblasts and inactivation of bacterial isolates from arthroplasty patients: potential for new disinfection applications?

“…Although not as bactericidal as UV light, 405 nm light has advantages including increased human safety due to its lower photon energy (Blatchley and Peel, 1991). Previous studies have demonstrated that this 405 nm blue light can inactivate various bacteria, including Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), S. epidermidis and Escherichia coli (Guffey and Wilborn, 2006;Maclean et al, 2008a;Maclean et al, 2009). The mechanism of bacterial inactivation is thought to be by photostimulation of endogenous intracellular porphyrins, which leads to the generation of reactive oxygen species (ROS) (Orenstein et al, 1997;Papageorgiou et al, 2000;Guffey and Wilborn, 2006;Maclean et al, 2008b).…”

Decontamination of the Hospital Environment: New Technologies for Infection Control

“…The antimicrobial action of 405nm violet-blue light is caused by oxidative damage resulting from the photo-excitation of porphyrin molecules within exposed microorganisms, and antimicrobial activity is broad, affecting a wide range of clinically-relevant organisms, including MRSA, C. difficile, and A. baumannii [61]. Bacteria, bacterial biofilms, fungi, yeast and bacterial endospores are all susceptible to inactivation, however, as expected, bacterial spores display resilience and require significant doses of light to initiate inactivation [62][63][64].…”