Targeting resistant Staphylococcus aureus biofilm with organic acids: uncovering the biofilm disinfection mechanism.

This study examines the effects of ascorbic, acetic, citric, and lactic acids on resistant S. aureus, assessing planktonic growth using minimal inhibitory (MIC) and bactericidal concentrations, and evaluating mature biofilms for viability, biomass, enzyme activity, membrane integrity and stress. We found the lowest antimicrobial potential for acetic acid, followed by ascorbic acid, citric acid and lactic acid. Treatment of mature biofilms showed a reduction of up to 3 log CFU mL-1 for lactic acid, while other organic acids were less effective. Lactic acid was also the most effective in reducing biofilm biomass by up to 33%, indicating potential for combination with other antibacterial compounds. The crystal violet staining confirmed a reduction in biomass regarding the non-treated samples. Iodonitrotetrazolium chloride assay showed a decrease in metabolic activity, with the highest formazan reduction (88%) observed with acetic acid. Live/dead staining indicated increased cell death at higher concentrations (9 MIC), with lactic acid causing the most severe membrane damage. In addition, intracellular stress increased with acid concentration. These findings reveal not only differential biofilm-targeting effects among common organic acids but also highlight the translational potential of lactic and acetic acids as cost-effective strategies to control resistant S. aureus in clinical and industrial settings, providing a foundation for future therapeutic and preventive applications.