| Background and ObjectiveC.albicans is the major pathogen for hospital-acquired fungal infections in humans. This opportunistic pathogen asymptomatically colonizes many areas of the human healthy individuals. The widespread use of antifungal agents results in the emergence of drug-resistant C.albicans among previously drug-susceptible populations. One of the main factors of drug tolerances is their flexibility in adapting to different environments and adherent to the surface and growing in microbial populations known as biofilms. The clinical treatment of C.albicans infection becomes more difficult with the emergengce of biofilms. Biofilm-grown C.albicans cells are highly resistant to antifungal agents such as fluconazole, nystatin, amphotericin B, and chlorhexidine. Consequently, there is an urgent need for the development of new antifugal therapy. Blue light is commonly used to treat acne in clinic, however, in recent years, Blue light, particularly in the wavelength range of 405-470 nm, has been used to kill other various pathogenic bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, Methicillin-resistant Staphylococcus aureus and so on. In the present study, we discuss the usefulness of blue light treatment for both planktonic and biofilm C.albicans infection in vitro and mouse skin wound infection model in vivo.Methods1.450-470 nm visible light inactivation of planktonic C.albicans in vitro Tablet coated plate method to evaluate antifungal effect of 0, 12, 60, 120, 240J/cm2 energy density of blue light. Flow cytometry to assess antifungal effect of 240J/cm2 energy density of blue light after treatment 0.5h, 1h, 2h, respectively.2.450-470 nm visible light treatment of C.albicans in biofilm in vitro Identification of C.albicans biofilms in vitro;matured biofilms were divided into blank group and light group. Light group was irradiated with 240J/cm2 blue light. Then two groups stained by Live/Dead stain. Confocal laser scanning microscope(CLSM) was applied to estimate the antifungal effect of blue light.3.450-470 nm visible light therapy for C.albicans infection in mouse skin wound24 nude mice were randomly divided into three groups, Negative control group(C.albicans-, light-), Positive control group(C.albicans+, light-), Light treated group(C.albicans+, light+). Skin 1.0cm x 1.0cm full-thickness abrasion was made on the back surface of each mouse. The surface of each wound of positive control group and light treated group was inoculated with 20 ul suspension containing 1x109 CFU/ml of C.albicans. Light treated group was irradiated with 240J/cm2 blue light in 1d?2d?3d. Tablet coated plate method to evaluate antifungal effect of blue light. We measured the body weight of each mouse and the skin abrasion aera of each mouse. Haematoxylin and Eosin staining of wound tissue to observe the histopathologic changes of each group in the process of wound healing.Results1.60J/cm2,120J/cm2,240J/cm2 blue light can kill C.albicans effectively in vitro. After 240J/cm2 blue light irradiated, the killing rate of 0.5h,1h and 2h had significant difference between two groups in the three time points(p<0.05).2.We found that C.albicans can form mature biofilm in 96-well plate in 3 day. After 240J/cm2 energy density of blue light irradiated, fungi death occurred in all the layers of the biofilm.3.240J/cm2 blue light reduced C.albicans infection significantly in mice skin wounds. In the positive control group mice, a more rapid weight loss pattern was observed than in the blue light treated ones. Blue light had a significant advantage in wound healing in C.albicans infected mice. Positive control group mice had a more tremendous amount of inflammatory cells infiltrating into tissue compared with both light treated group and negative control group.Conclusion450-470 nm visible light shows highly efficient killing planktonic and biofilm C.albicans in vitro and it also can be an alternative therapy for C.albicans infections in vivo. |
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