Combination of Amphotericin B and Flucytosine against Neurotropic Species of Melanized Fungi Causing Primary Cerebral Phaeohyphomycosis

Abstract

ABSTRACT Primary central nervous system phaeohyphomycosis is a fatal fungal infection due mainly to the neurotropic melanized fungi Cladophialophora bantiana , Rhinocladiella mackenziei , and Exophiala dermatitidis. Despite the combination of surgery with antifungal treatment, the prognosis continues to be poor, with mortality rates ranging from 50 to 70%. Therefore, a search for a more-appropriate therapeutic approach is urgently needed. Our in vitro studies showed that with the combination of amphotericin B and flucytosine against these species, the median fractional inhibitory concentration (FIC) indices for strains ranged from 0.25 to 0.38, indicating synergy. By use of Bliss independence analysis, a significant degree of synergy was confirmed for all strains, with the sum ΔE ranging from 90.2 to 698.61%. No antagonism was observed. These results indicate that amphotericin B, in combination with flucytosine, may have a role in the treatment of primary cerebral infections caused by melanized fungi belonging to the order Chaetothyriales . Further in vivo studies and clinical investigations to elucidate and confirm these observations are warranted.