Biofilm Development on Acrylic by Candida albicans Blastospores and Hyphae

Introduction: Candida albicans is a known aetiological agent of denture stomatitis. Candida hyphae have been shown to respond to their surroundings, growing directionally in response to stimuli including chemical signals and contact sensing. This characteristic is thought to be important in the penetration of denture soft lining materials and host epithelium. It has also been suggested that germ tube production can enhance adhesion and may therefore present benefits to the organism's establishment and survival on host /denture surfaces. Methods: Biofilms were grown in Sabouraud broth for 48h on abraded and un-abraded denture acrylic pieces from adhered C.albicans blastospores or hyphae. Biofilms were stained with calcofluor white and examined by confocal microscopy. Biofilms were removed by vortex mixing in phosphate buffered saline and filtered (0.2µm pore size). Filters were dried at 37˚c for 24h and dry weights recorded. Acrylic surfaces were stained with acridine orange and examined for remaining cells using fluorescence microscopy. Results: Biofilms grown from both cell types contained budding yeast cells, germ tubes, pseudo-hyphae and true hyphae. Biofilms grown from hyphal phase candida were thicker than those grown from blastospores and comprised an abundance of large hyphae. The difference in biofilm thickness was only significant on the un-abraded surfaces (p=<0.05). The mass of biofilms grown from hyphal phase candida was significantly greater (p=<0.05) than from blastospores on both surfaces. There was no significant difference in the numbers of cells remaining on the surfaces after removal. Conclusions: The early presence of hyphae in adhered Candida cells results in biofilms with greater mass. The significantly thicker biofilms grown from hyphae compared to blastospores on the un-abraded surfaces – but not on abraded surfaces - indicates that roughened surfaces enhance blastospore retention and biofilm formation. Future investigations will assess how the different biofilms are penetrated by denture cleansers. Funded by GlaxoSmithKline.