Standardized Method for In Vitro Antifungal Susceptibility Testing of <i>Candida albicans</i> Biofilms

TLDR

Candida albicans causes biomaterial‑related infections, forming biofilms that exhibit phenotypic traits distinct from planktonic cells and are highly resistant to antimicrobials, making such infections difficult to eradicate. The study reports a rapid, highly reproducible microtiter‑based colorimetric assay that measures metabolic activity of sessile cells via formazan reduction to test antifungal susceptibility of C. albicans biofilms. The assay was applied to C.

Abstract

Candida albicans is implicated in many biomaterial-related infections. Typically, these infections are associated with biofilm formation. Cells in biofilms display phenotypic traits that are dramatically different from those of their free-floating planktonic counterparts and are notoriously resistant to antimicrobial agents. Consequently, biofilm-related infections are inherently difficult to treat and to fully eradicate with normal treatment regimens. Here, we report a rapid and highly reproducible microtiter-based colorimetric assay for the susceptibility testing of fungal biofilms, based on the measurement of metabolic activities of the sessile cells by using a formazan salt reduction assay. The assay was used for in vitro antifungal susceptibility testing of several C. albicans strains grown as biofilms against amphotericin B and fluconazole and the increased resistance of C. albicans biofilms against these antifungal agents was demonstrated. Because of its simplicity, compatibility with a widely available 96-well microplate platform, high throughput, and automation potential, we believe this assay represents a promising tool for the standardization of in vitro antifungal susceptibility testing of fungal biofilms.