In vitro Antifungal Effects of Berberine Against spp. In Planktonic and Biofilm Conditions.

Purpose: Antifungal resistance associated with the extensive use of antifungals and biofilm formation presents major clinical challenges. Thus, new therapeutic strategies for fungal infections are urgently required. This study aimed to evaluate the in vitro antifungal effects of the natural bioactive alkaloid berberine against spp. in planktonic and biofilm conditions.

Methods: Using the CLSI M27-A3 reference method for broth dilution antifungal susceptibility testing of yeasts, the MICs for five standard strains comprised of (ATCC 10231, ATCC 90028), (ATCC 6258), (ATCC 90030), (MYA 646), and six clinical isolates (CLC1-CLC6) were tested. The 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay was used to evaluate the inhibitory effects of berberine against biofilms. The optical density value at 490 nm was measured and illustrated using concentration-absorbance curves. Finally, the effects were quantified by confocal laser scanning microscopy (CLSM), and 3-dimensional reconstruction was performed. The viability inhibition rates, biofilm formation, and thickness decrease rates were tested and analyzed using independent-samples -test. The differences among the five strains were analyzed using one way ANOVA.

Results: The MICs for the five standard strains described above were 80, 160, 10, 20, and 40 μg/mL, respectively, which was similar to that of the clinical isolates, suggesting the stable, broad-spectrum antifungal activity of berberine. Berberine exerted concentration-dependent inhibitory effects against biofilms, which were enhanced with the maturation of biofilms. Berberine decreased the viability of biofilms, with inhibition rates by CLSM ranging from 19.89 ± 0.57% to 96.93 ± 1.37%. Following 3-dimensional reconstruction, the biofilms of the berberine-treated group displayed a poorly developed architecture, and the biofilm thickness decrease rates ranged from 15.49 ± 8.45% to 30.30 ± 15.48%.

Conclusion: Berberine exhibited significant antifungal activity in spp. The results provide a useful reference for multiple infections and biofilm infections associated with antifungal resistance. Therefore, berberine might have novel therapeutic potential as an antifungal agent or a major active component of antifungal drugs.