Synergy of fluconazole with human monocytes or monocyte-derived macrophages for killing of Candida species.

Possible synergy between fluconazole and monocyte-derived macrophages (MDM) for significant killing of Candida species and between fluconazole and monocytes for increased candidacidal activity were studied. Human serum in test medium (RPMI 1640 with 10% fresh autologous human serum) was highly fungistatic for Candida species. Fluconazole in test medium, even at high concentrations, was not fungicidal. Monocytes alone were fungicidal for all Candida species and synergized with fluconazole for increased killing of a fluconazole-sensitive and a fluconazole-resistant Candida albicans isolate. MDM obtained by culturing for 3 or 5 days were not significantly fungicidal for C. albicans but could synergize with fungistatic fluconazole for significant killing. MDM alone killed Candida krusei and Candida glabrata but did not synergize with fluconazole for significantly increased killing. These results, which demonstrate synergy of fluconazole and mononuclear phagocytes for killing, help explain the in vivo efficacy of fluconazole against candidiasis.