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.

Figures

FIG. 1.

Emission spectrum of 99-LED array.

FIG. 2.

Results of 405-nm light inactivation of MRSA and other medically important gram-positive bacteria at an irradiance of 10 mW cm−2.

FIG. 3.

Results of 405-nm light inactivation of a range of medically important gram-negative bacteria at an irradiance of 10 mW cm−2. Also included is the inactivation curve for the gram-positive bacterium E. faecalis, which shows a significant inactivation effect after a 240-min exposure.

FIG. 4.

Results of 405-nm light inactivation of S. aureus suspensions with different starting populations.