FUNGICIDAL ACTION OF DISINFECTANTS ON Candida parapsilosis BIOFILMS AND THEIR RELATION TO PERSISTENT CELL FORMATION

Abstract

Candida species can cause hospital-acquired infections due to their ability to inhabit and form biofilms on the host or on abiotic surfaces. Despite health establishments prioritizing the application of disinfection programs to minimize the risk of contamination, the literature shows little efficiency of disinfectants in these environments, a fact related to the presence of biofilms, which are less susceptible to biocides, antibiotics and physical stress. Furthermore, conventional treatment, disinfection and cleaning strategies do not proficiently deal with biofilm related problems such as persistent infections and ongoing contamination of facilities. In this context, this study proposes to relate the effect of chlorhexidine and peracetic acid on the formation of persistent cells in Candida parapsilosis biofilms after exposure to the same disinfectants. In addition, the fungicidal action of chlorhexidine will be evaluated in biofilms formed on catheters. Environmental strains of C. parapsilosis stricto sensu, forming biofilms, will be used. Commercial preparations of disinfectants will be diluted to use concentrations in distilled water and sterilized. For the study of persistent cells, biofilms (B1) will be formed in 96-well microplates, subjected to high doses of disinfectants and the surviving cells will be recovered by plating on agar. New biofilms (B2) will be formed from the surviving cells and again subjected to the same treatment with disinfectants. Biomass determination by crystal violet methodology, the minimum inhibitory concentration by broth microdilution and the minimum fungicidal concentration will be carried out in the two cell populations - B1 and B2 and compared. In addition, biofilms will be formed on polytetrafluoroethylene catheters and treated with chlorhexidine. After exposure, the cells will be harvested, stained with propidium iodide and the number of dead cells will be quantified with the aid of an epifluorescence microscope. Knowledge of the effectiveness of disinfectants used in the hospital routine on C. parapsilosis biofilms can increase the knowledge of microbial tolerance to environmental stresses, which has been largely underestimated.