Author:

Abstract:

Candida albicans is the major cause of fungal infections in human, affecting even healthy individuals as it easily colonizes oral and vaginal mucosae where it progresses as a biofilm. The limited amount of successful anti-biofilm therapy options has led to failure of treatment, emergence of drug resistance and disease recurrence. To improve current treatments, we are looking for potentiators of the azole-type antifungal drug miconazole. On one hand, we randomly screened 1600 compounds of a drug repositioning library in combination with a sub-inhibitory concentration of miconazole for increased activity against mature C. albicans biofilms. Hits of the screen were molecules with diverse medical applications, including several artemisinins, used to treat malaria. On the other hand, we performed a comprehensive transcriptome analysis (using RNA-sequencing) of mature C. albicans biofilms treated with miconazole to reveal tolerance mechanisms induced upon application of this drug. Combination of an inhibitor of such tolerance pathway with miconazole could potentially lead to increased activity against C. albicans biofilms. Many of the differentially expressed genes were related to known defence mechanisms against azoles such as induction of drug efflux pumps. Interestingly, also new potential tolerance targets were identified. For the most promising hits from the screen and for selected inhibitors of miconazole-induced biological processes, we performed checkerboard analyses and calculated the fractional inhibitory concentration index, thereby revealing several synergistic combinations. We conclude that transcriptome analysis of drug-treated microbial populations can successfully identify tolerance targets for potentiation. However, randomly screening bio-active compound libraries seemed more efficient in this study.