Review of the Comparative Susceptibility of Microbial Species to Photoinactivation Using 380-480 nm Violet-Blue Light.

Rachael M Tomb,Tracy A White,Scott J Macgregor,John G Anderson,Michelle Maclean,John E Coia

doi:10.1111/php.12883

Rachael M Tomb, Tracy A White + Show 4 more

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https://doi.org/10.1111/php.12883

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Abstract

Antimicrobial violet-blue light is an emerging technology designed for enhanced clinical decontamination and treatment applications, due to its safety, efficacy and ease of use. This systematized review was designed to compile the current knowledge on the antimicrobial efficacy of 380-480 nm light on a range of health care and food-related pathogens including vegetative bacteria, bacterial endospores, fungi and viruses. Data were compiled from 79 studies, with the majority focussing on wavelengths in the region of 405 nm. Analysis indicated that Gram-positive and Gram-negative vegetative bacteria are the most susceptible organisms, while bacterial endospores, viruses and bacteriophage are the least. Evaluation of the dose required for a 1 log10 reduction of key bacteria compared to population, irradiance and wavelength indicated that microbial titer and light intensity had little effect on the dose of 405 nm light required; however, linear analysis indicated organisms exposed to longer wavelengths of violet-blue light may require greater doses for inactivation. Additional research is required to ensure this technology can be used effectively, including: investigating inactivation of multidrug-resistant organisms, fungi, viruses and protozoa; further knowledge about the photodynamic inactivation mechanism of action; the potential for microbial resistance; and the establishment of a standardized exposure methodology.

Highlights

Visible light inactivation of microorganisms has been associated with photodynamic inactivation (PDI)
Comparisons were made between several species of bacteria due to the large number of results collected during the systematized review
The effect of population density and irradiance of 405 nm light on the average dose for 1 log10 reduction was compared between E. coli, L. monocytogenes, P. aeruginosa and S. aureus

Summary

Introduction

Visible light inactivation of microorganisms has been associated with photodynamic inactivation (PDI) This inactivation method utilizes exogenous photosensitizers such as methylene blue, rose bengal or cationic porphyrins, which in the presence of oxygen become excited when exposed to different wavelengths of light, including violet-blue (380–500 nm) and red (625–740 nm) [1,2,3,4,5]. Studies by Hamblin et al [10] indicated Helicobacter pylori could be inactivated by at least 99% following a dose of 20 J cmÀ2 of violet-blue 405 nm light The authors believed this was due to the presence of high levels of the intracellular porphyrins coproporphyrin and protoporphyrin IX, which produce ROS upon illumination. Studies by Maclean et al [12,13] demonstrated the oxygen enhancement of the visible light inactivation of S. aureus—supporting the theory that inactivation was via a photodynamic process—and that within the violet-blue light region, antimicrobial activity peaked with exposure to wavelengths of around 405 nm (Æ10 nm)

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