Evaluation of antifungal and antibiofilm activity of commercial mouthwashes sold in Türkiye against oral biofilm-forming yeasts: an in vitro microbiological study

Introduction: In recent years, the use of mouthwashes has become quite common in various situations, from bad breath to treating minor infections. Although oral care products have a broad spectrum of antibacterial activity, little is known about their antifungal properties, and studies on antifungal and antibiofilm activity on oral-isolated Candida isolates are limited. Objective: This study aimed to assess the antifungal and antibiofilm activities of the best-selling mouthwashes in Türkiye against yeast strains isolated from the mouth, known for their strong biofilm production. Methods: This study investigated the antifungal and antibiofilm activity of twenty-five commercially available types of mouthwash against 19 Candida sp. and 1 Pichia manshurica strains isolated from the oral cavity of 18- 25-year-olds. Results: It was determined that twelve mouthwashes containing cetylpyridinium chloride had antifungal activity. It was determined that MIC values of mouthwashes varied between 0.20 and 1.56 µL/mL. Also, the effect of mouthwashes on mature biofilm and biofilm formation was evaluated according to MIC values. It was determined that mouthwashes are remarkably effective during biofilm formation but have little effect on mature biofilm structure. Conclusion: This study demonstrates that mouthwashes may possess not only antibacterial but also antifungal properties. Mouthwashes containing cetylpyridinium chloride have been shown to exhibit antifungal activity against oral Candida species, as confirmed by MIC values. Furthermore, these mouthwashes strongly inhibit biofilm formation but have a limited impact on the structure of mature biofilms. These findings suggest that mouthwashes should undergo evaluation for their antifungal effects and may play a significant role in clinical applications, particularly due to their biofilm-inhibiting characteristics.