Overcoming Candida albicans biofilm drug resistance via azole-sophorolipid synergy

Antimicrobial resistance is a momentous global threat, demanding innovative approaches to combat drug-resistant pathogens. As a prevalent fungal pathogen, Candida albicans exhibits increasing resistance to conventional antifungals, especially the azoles. This study explores a novel approach combining sophorolipids (SLs), a glycolipid biosurfactant, with clinical azoles, including fluconazole (FLZ), itraconazole (ITZ), and ketoconazole (KCZ), against C. albicans biofilms. SLs from the yeast Starmerella riodocensis exhibited promising metabolic reduction and antibiofilm activity against Candida biofilms, with a biofilm inhibitory concentration (BIC₅₀) of 512 mg/L. Among the tested azoles, ITZ exhibited the highest antibiofilm efficacy, prompting further investigation of SLs combinations. The ITZ-SLs combination markedly enhanced antibiofilm activity against preformed biofilms, with ITZ and SLs concentrations reduced by 16-fold and 4-fold, respectively, compared with their individual treatments (achieving a BIC₅₀ of 1 mg/L ITZ and 128 mg/L SLs). Quantitative real-time polymerase chain reaction analysis revealed significant downregulation of essential biofilm-associated genes such as BCR1, EFG1, and CDC28, demonstrating SLs's ability to inhibit various stages of biofilm development and stability. Thus, the synergy observed with azole drugs, particularly ITZ and SLs, was highly effective in biofilm removal, highlighting the compatibility of anti-biofilm biosurfactant SLs with some antifungal agents.