The role of saliva and serum in Candida albicans biofilm formation on denture acrylic surfaces

The long term effect of either a salivary or a serum pellicle on Candida albicans biofilm formation on denture acrylic surfaces was investigated both by quantifying the ATP (adenosine triphosphate) content of the resultant biofilms and by scanning electron microscopy. When the biofilm formation on saliva-coated acrylic strips was examined, the yeasts initially colonised this surface at a slower rate than the controls although with increasing incubation time, at 72 h, the ATP content was almost ten-fold higher than the protein-free control strips. Ultrastructural studies revealed this to be due to cell aggregation and hyphal emergence, phenomena not observed in the controls. As compared with the control strips, biofilm activity of the serum-coated strips was almost 100-fold greater within 48 h incubation, and scanning electron microscopy revealed multilayer blastospore-blastospore co-adhesion, germ tube, hyphal and pseudohyphal emergence and blastospore-hyphal coadherence. Further immunocytochemical observation revealed that concanavalin-A binding material and fibronectin were involved in biofilm formation on both saliva and serum coated specimens and, in addition, mannan-binding protein and protein-A binding material also contributed to the biofilm formation on serum coated specimens.