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1. Introduction
Despite enormous investments in public health research, bacterial pathogens transmitted in food, water, and from other environmental sources remain a major cause of illness in both the developed and developing world. Examples of such ubiquitous pathogens include enteric Gram-negative bacteria such as Salmonella, Escherichia, and Shigella which continue to cause significant diarrhoeal infections worldwide [1]. The foodborne pathogen Listeria monocytogenes also, has significant impact on health statistics through its propensity for causing serious illness in the immunocompromised [2]. Actinobacteria from the Mycobacterium genus are also a major cause of human morbidity and mortality and pathogens from the Mycobacterium tuberculosis complex such as M. bovis and M. tuberculosis remain amongst the most serious causes of infective disease worldwide [3].
Whilst many traditional decontamination methods give sterling service, they are not without limitations. Problems associated with product/material damage related to the use of physical methods and development of microbial resistance as well as the formation and persistence of potentially harmful residues are longstanding issues related to the use of chemical disinfectants such as sodium hypochlorite, ozone, and H2O2 [4–7]. Mycobacteria have innate resistance to chemical decontamination as they possess an unusual cell envelope containing peptidoglycan, arabinoglycan, and mycolic acid. This restricts the passage of many chemicals/drugs across the cell envelope, contributing to the hardiness of this microorganism [8, 9].
In response to the ongoing challenges presented by established and emerging pathogens and to provide additional or alternative approaches to microbial control, considerable interest has developed concerning novel methods of disinfection and decontamination.
Such alternative methods of decontamination include continuous and pulsed UV light, which has been shown to be highly germicidal. However, limitations such as poor transmissibility, degradative effects on materials, and potential carcinogenic effects in humans mean that there are restrictions in its use [10–13]. A safe, non-UV, light-based decontamination technology termed high-intensity narrow-spectrum (HINS) light has been recently described. HINS light of 405 nm stimulates endogenous microbial porphyrin molecules to produce oxidising reactive oxygen species (ROS), predominantly singlet oxygen (1O2) that damages cells leading to microbial death [14–16]. Specifically 405 nm light has been shown to be capable of inactivating a range of predominantly nosocomial pathogens and also Gram negative food-related pathogens [17–22].
This study further...