Tyrosol Activity against Pre-formed Oral Biofilms

Objectives: This study aimed to investigate the activity of tyrosol against pre-formed biofilms of Streptococcus mutans alone and in association with Candida albicans and Candida glabrata, both formed on specimens of acrylic resin (AR) and hydroxyapatite (HA).
Methods: AR and HA specimens were placed into 24-well plates and inoculated with S. mutans alone or in association with C. albicans and C. glabrata. After 24 h, pre-formed biofilms were treated with tyrosol (diluted in artificial saliva (AS)) at 100 and 200 mM twice a day for one minute, during 3 days, totaling 96-h biofilms. Chlorhexidine gluconate (CHG) and AS without tyrosol were used as positive and negative controls, respectively. Tyrosol activity was evaluated through the counting of colony-forming units (CFUs) and composition of biofilms’ extracellular matrix. Biofilm structure was observed by scanning electron microscopy (SEM). Data were analyzed by one- and two-way ANOVA, followed by Tukey’s and Holm-Sidak’s tests (p<0.05).
Results: For all tested biofilms on both surfaces, only CHG was able to promote significant reductions in the number of CFUs (ranging from 0.5 to 3.5-log₁₀). Tyrosol at 200 mM promoted a significant increase in the protein content of single biofilm of S. mutans. Regarding carbohydrate content, no significant differences were observed among the treatments. SEM observations confirmed that pre-formed biofilms were structurally unaffected by tyrosol treatments.
Conclusions: Tyrosol did not show effect against pre-formed biofilms of S. mutans alone or in association with Candida species. The antibiofilm effect of tyrosol in combination with conventional antimicrobials against a large number of strains should be explored in future investigations.