Influence of Fluconazole Resistance and Susceptibility on Candida-Streptococci Aggregation Dynamics.

Objective: To investigate the interaction between fluconazole-resistant (Flu-R) and -susceptible dose-dependent (Flu-SDD) isolates of Candida albicans and Candida glabrata with oral streptococci, exploring autoaggregation, coaggregation, and the impact of streptococcal biofilm-secreted components on Candida biofilms.

Methods: Autoaggregation and coaggregation of Candida Flu-R and Flu-SDD isolates with streptococci (S. mutans, S. gordonii, and S. sanguinis) were assessed using an optical density assay. The inhibitory effects of streptococcal biofilm-secreted components on Candida biofilms were examined, quantifying biofilm inhibition by crystal violet staining and assessing viability through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Statistical analysis of the data was done by one-way ANOVA, considering a p-value of < 0.05 as significant.

Results: Flu-R C. albicans exhibited higher autoaggregation (71%) than Flu-SDD (62%), both surpassing Streptococcus spp. (32%-49%). Flu-R and Flu-SDD C. glabrata had less autoaggregation ability than C. albicans (p < 0.05). Coaggregation increased steadily, with Flu-SDD C. albicans exhibiting the highest coaggregation with S. mutans (69% ± 8% at 2 h). Flu-R strains showed significant coaggregation differences with streptococcal species (p-values 0.05-< 0.001). Biofilm inhibition was significant in Candida Flu-R and Flu-SDD isolates treated with streptococcal biofilm supernatants. Supernatants of all three streptococcal species decreased Flu-R C. albicans viability (1.15-2.15-fold).

Conclusions: Fluconazole susceptibility/resistance significantly influences aggregation and biofilm formation with oral streptococci. Streptococcal biofilm supernatants hinder Candida strains' growth and viability, suggesting implications for colonization, biofilm formation, and oral infections.