Review of the comparative susceptibility of microbial species to photoinactivation using 380-480 nm violet-blue light

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 systematised review was designed to compile the current knowledge on the antimicrobial efficacy of 380-480 nm light on a range of healthcare and food related pathogens including vegetative bacteria, bacterial endospores, fungi and viruses. Data was compiled from 79 studies, with the majority focussing on wavelengths in the region of 405 nm. Analysis indicated that Gram positive and negative vegetative bacteria are the most susceptible organisms, whilst 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 titre 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 standardised exposure methodology.