Antifungal Activity of Aureobasidin A in Combination with Fluconazole against Fluconazole-Resistant Candida albicans 

Background: Aureobasidin A is known as a cyclic depsipeptide antibiotic with toxic effects against yeasts such as Candida spp at low concentration. Combination therapy is used as a conventional treatment for fungal infections, especially drug-resistant cases. The current study aimed to investigate the combined effects of fluconazole and Aureobasidin A on fluconazole-resistant C. albicans isolates using broth microdilution method. Materials & Methods: Antifungal activity of Aureobasidin A (AbA) compared to fluconazole against C. albicans ATCC ۷۶۶۱۵ strain was determined using the standardized broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI, document M۲۷-Ed۴) guidelines. The checkerboard method was used to test the combined effects of Aureobasidin A and fluconazole. The synergy, indifference, and antagonism were defined based on the fractional inhibitory concentration values below ۰.۵, ۰.۵-۴, and more than ۴ μg/mL, respectively. Findings: MIC۵۰ and MIC۹۰ evaluations of Aureobasidin A and fluconazole were done at concentrations of ۰.۲۵-۲ and ۳۲-۶۴ μg/mL against C. glabrata isolates, respectively. The synergy between fluconazole and Aureobasidin A was observed against Candida isolate. A reduced MIC was demonstrated against C. albicans isolate when fluconazole was combined with Aureobasidin A at ۴ to ۰.۱۲ μg/mL concentrations. Conclusion: The present study findings revealed that Aureobasidin A combined with fluconazole exhibited potent inhibitory effects against fluconazole-resistant C. albicans isolates. Further studies is recommended to investigate the synergistic effects of Aureobasidin A and other antifungal drugs.  

Keywords:

Minimum inhibitory concentration (MIC) , Fluconazole-resistance , Aureobasidin A , Candida albicans