Antimicrobial blue light inactivation ofCandida albicans:In vitroandin vivostudies

Abstract

Fungal infections are a common cause of morbidity, mortality and cost in critical care populations. The increasing emergence of antimicrobial resistance necessitates the development of new therapeutic approaches for fungal infections. In the present study, we investigated the effectiveness of an innovative approach, antimicrobial blue light (aBL), for inactivation of Candida albicans in vitro and in infected mouse burns. A bioluminescent strain of C. albicans was used. The susceptibilities to aBL (415 nm) were compared between C. albicans and human keratinocytes. The potential development of aBL resistance by C. albicans was investigated via 10 serial passages of C. albicans on aBL exposure. For the animal study, a mouse model of thermal burn infected with the bioluminescent C. albicans strain was used. aBL was delivered to mouse burns approximately 12 h after fungal inoculation. Bioluminescence imaging was performed to monitor in real time the extent of infection in mice. The results obtained from the studies demonstrated that C. albicans was approximately 42-fold more susceptible to aBL than human keratinocytes. Serial passaging of C. albicans on aBL exposure implied a tendency of reduced aBL susceptibility of C. albicans with increasing numbers of passages; however, no statistically significant difference was observed in the post-aBL survival rate of C. albicans between the first and the last passage (P>0.05). A single exposure of 432 J/cm(2) aBL reduced the fungal burden in infected mouse burns by 1.75-log10 (P=0.015). Taken together, our findings suggest aBL is a potential therapeutic for C. albicans infections.

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

“…For P. aeruginosa, when 110 J/cm 2 aBL was delivered, an approximately 7.64-log 10 CFU inactivation was achieved (Dai et al, 2013b). For A. baumannii and C. albicans , over 4-log 10 CFU were inactivated after an exposure of 70 J/cm 2 aBL (Zhang et al, 2016; Zhang et al, 2014). The inactivation curves of the above pathogens approximately followed first-order kinetics (Xiong et al, 1999), a linear relation between the log-transformed cell survival fraction log 10 and the aBL exposure.…”

Methylene Blue and Hydrogen Peroxide for Photodynamic Inactivation in Root Canal - A New Protocol for Use in Endodontics

“…Also, the bioluminescence method is a non-invasive technique; therefore, sequential images could be obtained for each sample, allowing statistical analysis without any inter-sample variation. The method is an alternative to traditional in vitro culture methods using paper point sampling and quantitative culture and has been used in different studies to evaluate infections and bacterial reduction in vitro and in animal models (3, 6, 13, 17, 26, 17, 27). …”

The antimicrobial effect of blue light: What are behind?

“…No development of aBL resistance was observed after 10-20 cycles of repeated aBL exposures. 25,27,28 Other studies demonstrated that aBL did not cause significant damages to host cells and did not impair wound healing. 18,26,28,34,39,40 In this issue of Virulence, Fila et al 22 investigated the effectiveness of aBL inactivation of Pseudomonas aeruginosa using a panel of wide types and clinical strains, including multidrug-resistant and extensively drug-resistant strains.…”

“…44,45 In the studies of our laboratory, we observed via transmission electron microscopy that sublethal exposures of aBL induced cell wall damage in microbes. 27,30 This may enhance the penetration of antibiotics into microbial cells and subsequently potentiate the inactivation of microbes. Another possibility leading to aBL-induced hyper-susceptibility to antibiotics is the oxidative stress-induced under-expression of drug resistance genes.…”

“…14,23,25,26,30,35 It was also observed that pathogenic microbes are less able to develop resistance to aBL than to conventional antibiotics. Our group recently performed several studies by exposing Pseudomonas aeruginosa, 25 Acinetobacter baumannii, 28 Candida albicans 27 or Escherichia coli (unpublished), to repeated cycles of sub-lethal aBL. No development of aBL resistance was observed after 10-20 cycles of repeated aBL exposures.…”