Photodynamic inactivation of normal and antifungal resistant Candida species

Summary 

Background

Susceptibility of bacterial and fungal species to the photodynamic killing effects of various photosensitizing dyes has received increasing attention. In the oral cavity oral candidiasis is primarily caused by Candida albicans. Evidence suggests that Oropharyngeal Candidiasis, found frequently in patients with immunodeficiency, present with mixed Candida organisms and are more difficult to treat than those solely due to C. albicans. In the present study we demonstrate the ability to efficiently kill antifungal resistant isolates of Candida using Photofrin induced PDT.

Methods

Candida strains from the ATCC as well as fluconazole and amphotericin B resistant and sensitive isolates from adults with AIDS were grown cultures and grown under standard conditions. Photofrin was added to appropriate cultures as dictated by experimental design. Light was delivered to assigned cultures using a 630nm laser source at a power density of 150mW/cm², for appropriate time to deliver 45–135J/cm². Colony forming assays were used to determine survival.

Results

After illumination cultures treated with Photofrin had significant reduction in colony forming ability at all light doses examined. Isolates from AIDS patients which had demonstrated antifungal resistance showed equivalent sensitivity to photodynamic killing as did control ATCC cultures of the same strain.

Conclusion

This study demonstrates Photofrin induced PDT can eliminate Candida species with significant efficiency as revealed by colony forming ability. Further Candida isolates from AIDS patients that had demonstrated fluconazole and amphotericin B resistance were equally susceptible to photodynamic killing.

Keywords: PDT, Candida, Antifungal resistance, AIDS