Effects of fluorides on Candida albicans

To assess whether a short exposure of Candida albicans to commonly used fluorides would affect growth, cell surface hydrophobicity, and adherence to buccal epithelial cells.

Candida albicans ATCC 90028 and 11 clinical isolates were used. Minimal inhibitory concentrations (MICs) of sodium fluoride (NaF) and of an amine fluoride / stannous fluoride combination (AmF / SnF2) were determined. Yeasts were exposed to MICs of tested agents for 1 h. Subsequently, their growth was recorded spectrophotometrically. Their cell surface hydrophobicity was assessed with n-hexadecane. Adherence to buccal epithelial cells was determined microscopically. Phosphate buffered saline (PBS) and chlorhexidine digluconate (CHX) served as controls. All results were analyzed by one-way ANOVA.

MICs of AmF / SnF(2) and CHX varied between 1 and 4 microg ml(-1), whereas those of NaF were 15 000 microg ml(-1). Statistically significant growth inhibition was detected after AmF / SnF(2) (OD(24 h) +/- SD 0.457 +/- 0.059) and CHX (0.175 +/- 0.065) in comparison with PBS (0.925 +/- 0.087) and NaF (0.813 +/- 0.081). All strains demonstrated uniform behavior. Only minor changes in cell surface hydrophobicity and adherence to buccal epithelial cells (BEC) were detected.

Growth inhibition of AmF / SnF(2) was comparable with that of CHX whereas NaF had a weaker effect. Exposure to the fluorides did not seem to alter the cell surface hydrophobicity nor adherence to BEC.