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Proceedings Paper

Oxidative stress of photodynamic antimicrobial chemotherapy inhibits Candida albicans virulence
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Paper Abstract

Photodynamic antimicrobial chemotherapy (PACT) is based on the principal that microorganisms will be inactivated using a light source combined to a photosensitizing agent in the presence of oxygen. Oxidative damage of cell components occurs by the action of reactive oxygen species leading to cell death for microbial species. It has been demonstrated that PACT is highly efficient in vitro against a wide range of pathogens, however, there is limited information for its in vivo potential. In addition, it has been demonstrated that sublethal photodynamic inactivation may alter the virulence determinants of microorganisms. In this study, we explored the effect of sublethal photodynamic inactivation to the virulence factors of Candida albicans. Methylene Blue (MB) was used as photosensitizer for sublethal photodynamic challenge on C. albicans associated with a diode laser irradiation (λ=660nm). The parameters of irradiation were selected in causing no reduction of viable cells. The potential effects of PACT on virulence determinants of C. albicans cells were investigated by analysis of germ tube formation and in vivo pathogenicity assays. Systemic infection was induced in mice by the injection of fungal suspension in the lateral caudal vein. C. albicans exposed to sublethal photodynamic inactivation formed significantly less germ tube than untreated cells. In addition, mice infected with C. albicans submitted to sublethal PACT survived for a longer period of time than mice infected with untreated cells. The oxidative damage promoted by sublethal photodynamic inactivation inhibited virulence determinants and reduced in vivo pathogenicity of C. albicans.

Paper Details

Date Published: 17 February 2011
PDF: 7 pages
Proc. SPIE 7887, Mechanisms for Low-Light Therapy VI, 78870B (17 February 2011); doi: 10.1117/12.876598
Show Author Affiliations
Ilka Tiemy Kato, Instituto de Pesquisas Energéticas e Nucleares (Brazil)
Renato Araujo Prates, Instituto de Pesquisas Energéticas e Nucleares (Brazil)
George P. Tegos, The Univ. of New Mexico Health Sciences Ctr. (United States)
Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Medical School (United States)
Michael R. Hamblin, Wellman Ctr. for Photomedicine, Massachusetts General Hospital (United States)
Harvard Medical School (United States)
Harvard-MIT Division of Health Sciences and Technology (United States)
Martha Simões Ribeiro, Instituto de Pesquisas Energéticas e Nucleares (Brazil)


Published in SPIE Proceedings Vol. 7887:
Mechanisms for Low-Light Therapy VI
Michael R. Hamblin; Ronald W. Waynant; Juanita Anders, Editor(s)

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