Yeast or fungal infections can be painful and incredibly persistent. Candida albicans, the most common of all so-called opportunistic fungal infections (i.e., those that strike when the immune system is weak), is especially difficult to remove. Over-the-counter and prescription treatments usually take days to take effect, and many cases become resistant to the treatments. Invasive fungal infections have been linked with very high mortality rates ranging up to 90% in some immune-suppressed populations for opportunistic fungal pathogens such as Candida albicans (scientific name: C. albicans). Ironically, it is the overuse of antibiotics that sets the stage for many yeast infections.
Candida’s ability to develop resistance to antifungal treatment represents a huge barrier to the success of therapy. A protective coating, or biofilm, is considered paramount to the development of invasive fungal infections and treatment resistance. Very few antifungal treatments have been effective against fungal biofilms. The emergence of resistance and changes in the spectrum of Candida infections have led to increased interest in alternatives to antifungal drugs.
Photodynamic therapy (PDT) was discovered over a century ago by observing the killing of microorganisms when harmless dyes and visible light were combined. PDT involves the use of light-sensitive compounds (photosensitizers) in combination with harmless visible light of the correct wavelength. In the presence of oxygen, the photosensitizer then transfers energy or electrons to molecular oxygen, generating reactive oxygen species that are able to kill abnormal cells, including cancer and microbes.
Though PDT has mainly been developed as a cancer treatment, interest in the antimicrobial effects of PDT has been mounting in recent years. When PDT is used to kill microbes such as bacteria and yeast cells, it is often referred to as photodynamic inactivation, or PDI. In this article, our primary focus will be on using PDI to overcome yeast infections.
In a recent laboratory study, PDI achieved significant reductions in the viability of various species of yeast. The highest reduction in cell viability of the biofilms was achieved in C. albicans, C. tropicalis and C. glabrata. PDI also reduced the metabolic activity of biofilms by 62%, 76%, and 77% for C. albicans, C. tropicalis, and C. glabrata, respectively, as reported in the October 2013 issue of Biofouling.
An approach known as photodynamic antimicrobial chemotherapy (PACT) has been created as a potential antimicrobial therapy and as a new way to overcome resistance to antibiotics and antifungal treatments. In one PACT study, toluidine blue was used as the photosensitizer agent, as reported in the 1 November 2013 issue of Lasers in Medical Science. Incubation with this light-sensitizer for 1, 2, and 3 hours was able to reduce biofilm formation in C. albicans by 30, 50, and 62 percent, respectively.
Another recent study examined the PDI potential of two photosensitizers, hypericin (a compound isolated from St. John’s Wort) or 1,9-dimethyl methylene blue, or DMMB. Both agents were effective in killing C. albicans strains independent of their treatment resistance pattern. Hypericin was more efficient at low fungal concentration while DMMB was better at higher concentrations. The researchers state that “antimicrobial photodynamic therapy” constitutes an emerging alternative for the treatment of yeast infections, as reported in the 12 June 2013 issue of Mycoses.
Avoidance of sugar, refined carbohydrates, and other dietary modifications are a popular holistic treatment for yeast infection. In the context of antifungal drug treatments, strict dietary modifications can lead to changes in your body that cause Candida albicans to eventually die off. The addition of PDI could be the key to ultimately eradicating a Candida overgrowth situation that has become resistant to conventional treatment methods.
For another timely perspective on PDI’s immense potential , see “Defeating Biowarfare with Light”.
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Dovigo LN, Carmello JC, Carvalho MT, Mima EG, Vergani CE, Bagnato VS, Pavarina AC. Photodynamic inactivation of clinical isolates of Candida using Photodithazine(®). Biofouling. 2013 Oct;29(9):1057-67.
Rosseti IB, Chagas LR, Costa MS. Photodynamic antimicrobial chemotherapy (PACT) inhibits biofilm formation by Candida albicans, increasing both ROS production and membrane permeability. Lasers Med Sci. 2013 Nov 1. [Epub ahead of print]
Paz-Cristobal MP, Royo D, Rezusta A, Andrés-Ciriano E, Alejandre MC, Meis JF, Revillo MJ, Aspiroz C, Nonell S, Gilaberte Y. Photodynamic fungicidal efficacy of hypericin and dimethyl methylene blue against azole-resistant Candida albicans strains. Mycoses. 2013 Jun 12. [Epub ahead of print]
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