Repurposing Mouthwashes: Antifungal and Antibiofilm Abilities of Commercially Available Mouthwashes Against Candida spp.

<b>Background/Objectives</b>: The main objective was to evaluate and compare the antifungal efficacy against <i>Candida</i> spp. in commercially available mouthwashes distributed in the European market. Indeed, the solution to emerging infectious diseases may no longer lie in costly new drug development but rather in unlocking the untapped potential of existing substances. <b>Materials and Methods</b>: Eighteen mouthwashes, chosen based on their composition, were tested in vitro against ten <i>Candida</i> strains, including clinical isolates of oral origin and reference strains, in both planktonic and biofilm forms. The antifungal susceptibility testing was conducted using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) disc diffusion method and the evaluation of the kinetic growth in planktonic <i>Candida</i>. Biofilm reduction was determined by the evaluation of the minimal biofilm eradication concentration (MBEC). Scanning electron microscopy (SEM) analysis was performed to evaluate potential morphological alterations of <i>Candida</i> biofilms. <b>Results</b>: Most mouthwashes effectively reduced biomass production and colony-forming unit (CFU) count. Parodontax Extra showed the highest efficacy. In the disc diffusion assay, Gum Paroex 0.12% exhibited the largest average inhibition zone diameter. Some unusual trends in the data may be explained by a higher reaction of fungal cells and the release of excess biomass during co-incubation in higher concentration of mouthwashes. SEM images revealed significant morphological alterations. <b>Conclusion</b>: Mouthwashes containing chlorhexidine digluconate, either alone or in combination with cetylpyridinium chloride and other active compounds, emerged as a common factor among the most efficacious formulations. In vivo studies will be essential to validate these findings, but mouthwashes may serve as a valuable adjuvant in the treatment of oral candidiasis.