Improved efficacy of eugenol and <i>trans</i>-anethole in combination with octenidine dihydrochloride against <i>Candida albicans</i> and <i>Candida parapsilosis</i>

Candidiasis is a fungal infection caused by yeasts from the Ogenus Candida. Considering increasing antifungal resistance rates the activity was analyzed of natural compounds to eradicate Candida spp. The aim of the study was to check the antifungal activity of selected essential oil compounds (EOCs; thymol, menthol, eugenol [E], carvacrol, trans-anethole [TA]) alone, and in combination with octenidine dihydrochloride (OCT) against C. albicans and C. parapsilosis reference, and clinical strains.Investigated clinical isolates were obtained from skin wounds of patients treated for superficial wounds candidiasis. The following parameters were studied: antifungal susceptibility testing using the VITEK system, antifungal activity of EOCs alone and in combination with OCT using microdilution and checkerboard assays, antifungal efficacy of selected chemicals using time-kill curve assay, and changes in cell permeability in the presence of selected chemicals using crystal violet assay.Clinical isolates of C. albicans and C. parapsilosis were resistant to fluconazole and voriconazole. The highest inhibition activity against Candida isolates was observed for E. The OCT - TA and OCT - E combinations showed synergistic and additive activities against all strains, respectively. These combinations also appeared to affect the rate of yeast cell killing and increasing the permeability of Candida cells.The study indicates that E and TA potentially used in formulation with OCT might eradicate pathogenic yeasts; however, microbiological and clinical studies are still required.