Inhibition of quorum sensing in drug-resistant Staphylococcus epidermidis by flavaspidic acid BB

Abstract

Background: To investigate the effect of flavaspidic acid BB (BB) on biofilms and quorum sensing-related genes of drug-resistant Staphylococcus epidermidis (SE) and to provide a theoretical basis for the development of BB as a new type of quorum sensing inhibitor. Methods: The microdilution method was applied to screen 15 clinical isolates of S. epidermidis for drug-resistant S. epidermidis to be used as the test strain. The effects of BB on the biofilms of drug-resistant S. epidermidis at different growth stages were studied using the cell counting kit-8 assay and scanning electron microscopy. The gene expression of sigB, sarA, and luxS, regulators involved in quorum sensing of biofilm formation, was measured by PCR. Results: The minimum inhibitory concentrations of BB against 15 clinical strains of S. epidermidis ranged 11.67–66.67 µg/mL. BB significantly inhibited biofilm formation by drug-resistant SE06 in the aggregation and maturation stages, with an activity superior to those of mupirocin and fusidic acid (P < 0.05). At 40 µg/mL, BB reduced the secretion of extracellular polymers and promoted the disruption of biofilm structure. At 80 µg/mL, BB specifically interfered with the quorum sensing system of drug-resistant SE06 by downregulating sarA and luxS, thereby inhibiting this microbe’s biofilm formation. Conclusion: BB exhibited strong inhibitory activity against SE06 by suppressing biofilm formation and downregulating quorum sensing-related genes and was identified as a new potential quorum sensing inhibitor against S. epidermidis.