Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and Reduces In Vivo Pathogenicity

The objective of this study was to evaluate whether Candida albicans exhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells. C. albi-canswas exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs di-ode laser ( 660 nm, 75 mW/cm2, 9 to 27 J/cm2). In vitro, we evaluated APDI effects on C. albicans growth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility. In vivo, we evaluated C. albicans pathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI re-duced the growth rate and the ability of C. albicans to form germ tubes compared to untreated cells (P< 0.05). Survival of mice systemically infected with C. albicans pretreated with APDI was significantly increased compared to mice infected with un-treated yeast (P< 0.05). APDI increased C. albicans sensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole for C. albicanswas also reduced following sublethal MB-mediated APDI. However, none of those patho-genic parameters was altered in daughter cells of C. albicans submitted to APDI. These data suggest that APDI may inhibit viru