Oral Bacteria Modulate Candida Biofilm Formation

Objective: To evaluate the effect of four, aerobic and anaerobic oral commensal bacterial species on Candida albicans biofilm development. Methods: A single isolate of C. albicans 2560g, and two aerobes, Pseudomonas aeruginosa, Escherichia coli, and two anaerobes, Prevotella nigrescens, and Actinomyces israelii were used. Biofilm formation was quantified as the ability of Candida to grow in sessile form on polystyrene plastic surfaces pre-exposed to the foregoing bacteria. Scanning electron microscopy was used to confirm and visualise biofilm formation, and a viable cell count, together with a XTT reduction assay were used to quantify the sessile growth. Results: The latter two methods quantified well the biofilm growth with good correlation (r=0.667, P<0.001). A significant reduction in viability of C. albicans biofilm mass was noted when exposed to polystyrene plastic substrates coated with either P. aeruginosa, E. coli, P. nigrescens or A. israelii (P<0.05). Differing concentrations of bacteria on the substrate had a variable effect on Candida biofilm formation. Conclusions: Our data indicate that quantitative and qualitative nature of the bacteria on a substrate modifies the degree of Candida biofilm formation. This study was supported by the Research Grant Council, and the Committee for Research and Conference Grants of the University of Hong Kong, Hong Kong.