Virulence factors of different Candida species: reliability of microbiological methods and effect of photodynamic treatment

Abstract

The potential of Photodynamic Therapy (PDT) for Candida inactivation has been widely explored in the past few years. Promising results have been found with the use of curcumin as a photosensitizing agent to photoinactivate different Candida species. However, complete inactivation of yeast cells is not always achieved after just one PDT application, especially if biofilms were involved. If the application of PDT decreased the virulence of Candida cells, the use of this therapy could be safely recommended. Some microbiological techniques have been widely used to evaluate the expression of virulence factors in yeast cells. However, the reliability evaluation of these methods is crucial to reduce the possible biases that can certainly influence the variability of results, and consequently, the sample size and statistical power. This project aims to assess the reliability of measurements made for the analysis of virulence factors of the species C. albicans, C. glabrata, C. tropicalis and C. krusei, and the expression of these factors after exposure to curcumin-mediated PDT. An intra and inter-examiner reproducibility study will be performed and the sample size will be calculated after a pilot study. For those purposes, reference strains of C. albicans, C. glabrata, C. tropicalis and C. krusei will be selected. In order to allow the survival of the microorganisms after PDT, standard cell suspensions of each strain will be exposed to sublethal PDT. Then, the surviving yeast cells will be submitted to the following microbiological procedures in order to analyze the expression of the virulence factors: adhesion capacity, biofilm formation, and production of the enzymes proteinase and phospholipase. The control group will consist of suspensions that have not been exposed to PDT. (AU)