Additive antifungal activity of anidulafungin and human neutrophils against Candida parapsilosis biofilms

Objectives: To investigate the activities of two newer triazoles and two echinocandins combined with human phagocytes against Candida parapsilosis biofilms. Methods: An in vitro model of C. parapsilosis biofilms was used. Biofilms were grown on silicone elastomer discs in 96-well plates at 37°C for 72 h. Biofilms or planktonic cells were incubated with voriconazole, posaconazole, caspofungin or anidulafungin, at clinically relevant concentrations, and human phagocytes (neutrophils or monocytes) alone or in combination with each of the antifungal agents for a further 22 h. Fungal damage induced by antifungal agents and/or phagocytes was determined by XTT [2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)2H-tetrazolium-5-carboxanilide] metabolic assay. Results: Each of the antifungal agents alone and in combination with human phagocytes induced less damage against C. parapsilosis biofilms compared with planktonic cells. No antagonistic interactions between antifungal agents and phagocytes were found. Furthermore, anidulafungin, but not caspofungin, and neutrophils exerted additive activity against C. porapsilosis biofilms. Conclusions: Besides a lack of antagonistic interactions between newer antifungal agents and phagocytes, anidulafungin exerts additive immunopharmacological activity against C. parapsilosis biofilms.