The effect of oral commensal bacteria on candidal adhesion to human buccal epithelial cells in vitro

Abstract

The effect of Streptococcus sanguis, S. salivarius, Escherichia coli and Porphyromonas gingivalis on the adhesion of Candida albicans and C. krusei to human buccal epithelial cells (BEC) was investigated with a modified membrane filter system. The filters (12 μm diameter pores) acted as a support for the BEC which were pre-exposed to known concentrations of bacterial suspensions (for 45 min-1 h), and then re-incubated with standardised concentrations of yeast suspensions for various periods. The BEC with adherent yeasts were then transferred on to a glass slide, gram-stained and counted by light microscopy. Three of the four bacterial species significantly suppressed adhesion of C. albicans to BEC; S. sanguis had no effect. Both S. sanguis and S. salivarius suppressed adhesion of C. krusei to BEC pre-exposed to three different bacterial concentrations, although variable results were obtained with P. gingivalis and E. coli. Significant differences in the relative adhesion of C. albicans and C. krusei to BEC were also recorded. These results indicate that the adhesion of yeasts to BEC is modulated both by the composition and the quantity of the pre-existing bacterial flora on the BEC.