The combined utilization of Chlorhexidine and Voriconazole or Natamycin to combat Fusarium infections

Background Fusariumspecies are the fungal pathogens most commonly responsible for the mycotic keratitis, which are resistant to the majority of currently available antifungal agents. The present study was designed to assess the efficacy of a combination of low doses chlorhexidine with two other commonly used drugs (voriconazole and natamycin) to treatFusariuminfections. Results We utilized combinations of chlorhexidine and natamycin or voriconazole against 20 clinicalFusariumstrains in vitro using a checkerboard-based microdilution strategy. In order to more fully understand the synergistic interactions between voriconazole and chlorhexidine, we utilized aGalleria mellonellamodel to confirm the combined antifungal efficacy of chlorhexidine and voriconazole in vivo. We found that for voriconazole, natamycin, and chlorhexidine as single agents, the minimum inhibitory concentration (MIC) ranges were 2-8, 4-16, and > 16 mu g/ml, respectively. In contrast, the MIC values for voriconazole and chlorhexidine were reduced to 0.25-1 and 1-2 mu g/ml, respectively, when these agents were administered in combination, with synergy being observed for 90% of testedFusariumstrains. Combined chlorhexidine and natamycin treatment, in contrast, exhibited synergistic activity for only 10% of testedFusariumstrains. We observed no evidence of antagonism. Our in vivo model results further confirmed the synergistic antifungal activity of chlorhexidine and voriconazole. Conclusions Our results offer novel evidence that voriconazole and chlorhexidine exhibit synergistic activity when used to suppress the growth ofFusariumspp., and these agents may thus offer value as a combination topical antifungal treatment strategy.