Insights into betulinic acid as a promising molecule to fight the interkingdom biofilm Staphylococcus aureus–Candida albicans

The demand for antibiofilm molecules has increased for several years due to their potential to fight biofilm-associated infections such as those including the interkingdom Staphylococcus aureus - Candida albicans occurring in clinical settings worldwide. Recently, we have identified a pentacyclic triterpenoid compound identified as betulinic acid (BA) from invasive macrophytes with interesting antibiofilm properties. Our study aimed at providing insights into the mechanism of action of BA against the clinically relevant bi-species S. aureus-C. albicans biofilms. Microscopy examinations, flow cytometry and crystal violet assays confirmed that BA was effective for damaging mature S. aureus-C. albicans biofilms or inhibiting their formation, reducing biofilm biomass by 70% on average and without microbicidal activity. Results suggested an action of BA on cell membranes, inducing changes in properties such as composition, hydrophobicity and fluidity as observed in C. albicans, which may hinder the early adhesion step, the biofilm growth and the physical interactions of both microbial species. Further results of real-time PCR argued in favor of a reduction of S. aureus-C. albicans physical interaction due to BA by the modulation of biofilm-related gene expression as observed in early stages of biofilm formation. This study revealed the potential of BA as candidate agent for the prevention and treatment of S. aureus–C. albicans biofilm-related infections.