Beating Candida: New Light on Treatment Resistance


Photograph of Candida albicans under a microscope. 

Under normal circumstances, Candida albicans is a relatively benign yeast or fungus that grows in the intestinal tract. Candida can begin growing and spreading out of control, however, if the immune system becomes compromised and if antibiotics, chemotherapy, high-sugar diets, or some other factor disrupts the balance of gut bacteria that normally keep the yeast in check. About three out of every four women in Europe and North America will experience a yeast infection at some point in their lives.

These days, many younger women have recurring yeast infections.  Symptoms of Candida overgrowth or candidiasis may include fatigue, depression, mood swings, allergies, chemical sensitivities, itching, skin rashes, and digestive problems.  The problem may be excerbated by stress and poor dietary habits, especially those that include plenty of sugar and high-carbohydrate foods such as breads and pastries.

One of the promising alternatives to antifungal drugs is the light-based approach known as photodynamic therapy (PDT).  We now know that photosensitizers may become concentrated within abnormal cells, such as Candida and other fungal organisms.   When PDT is used to inhibit or kill microorganisms, it is also known as Photodynamic Inactivation.

Candida can invade the ear and throat area, and this infection, known as oropharyngeal candidiasis (OPC), is fairly common in people with compromised immune systems.  A study out of the Universidad Nacional de Rosario, in Rosario, Argentina, found that PDT was effective at killing various Candida strains.  Even at relatively low doses of photosensitizer, PDT was effective in killing Candida albicans isolated from OPC cases.  The authors propose that PDT may offer an alternative for OPC treatments, as reported online ahead-of-print in the 17 June 2014 issue of Phytomedicine.


Rendering Candida More Vulnerable:  Inactivating the Biofilm

Getting rid of a yeast infection is not a simple matter. Candida exhibits a powerful capacity to acquire resistance to antifungal drugs, and this poses a huge challenge to with conventional medicine.  Candida’s penchant for resisting treatment is thought to be due, in part to a protective microbial coating, or biofilm.  Few antifungal treatments have been effective against fungal biofilms, and yet it is precisely this mechanism that enables the development of more invasive fungal infections.

In a second study, researchers at the Center for Lasers and Applications in São Paulo, Brazil, focused on the problem  of Candida associated with root canal infection.  The authors were interested in using PDT as a way to complement conventional root canal disinfection methods and specifically to overcome the challenge of bacterial biofilms.

In this study, the photosensitizer used was methylene blue.  This was introduced into the canals and then exposed to a laser tip (using fiber optics) either in contact with pulp chamber or within the canal.  Light distribution was evaluated using a CCD camera, and the reduction in the microbial load was monitored using bioluminescence imaging.

The authors observed that PDT was indeed an effective way to inactivate Candida albicans and to eliminate the biofilm.  The diffuser fiber optics enabled optimal light treatment inside the curved root canals and significantly increased the efficacy of PDT, as reported in the 25 July 2014 issue of Lasers in Medical Science.

These findings were further reinforced by a separate study out of the University of Aveiro in Aveiro, Portugal. In this laboratory study, a porphyrin-based PDT was found to cause significant inactivation of the biofilms associated with Candida and other infections, as reported online ahead-of-print in the 12 August 2014 issue of Photochemistry and Photobiology.


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Postigo A1, Bulacio L2, Sortino M3. Photodynamic inactivation of oropharyngeal Candida strains. Phytomedicine. 2014 Jun 17. [Epub ahead of print]

Sabino CP, Garcez AS, Núñez SC, Ribeiro MS, Hamblin MR.  Real-time evaluation of two light delivery systems for photodynamic disinfection of Candida albicans biofilm in curved root canals. Lasers Med Sci. 2014 Jul 25. [Epub ahead of print]

Beirão S1, Fernandes S, Coelho J, Faustino MA, Tomé JP, Neves MG, Tomé AC, Almeida A, Cunha A. Photodynamic inactivation of bacterial and yeast biofilms with a cationic porphyrin. Photochem Photobiol. 2014 Aug 12. [Epub ahead of print]

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