The antibacterial and antivirulent potential of Hypericum lydium against Staphylococcus aureus: Inhibition of growth, biofilm formation, and hemolytic activity

Introduction: The Hypericum genus has attracted considerable attention in the last decades due to their pharmacologically important secondary metabolites. Despite various medical uses and prominent anti-inflammatory properties of Hypericum species, little is known about the antibacterial and antivirulent potential of Hypericum lydium. This study aimed to investigate these biological activities for the first time. Methods: Potential antibacterial activity of water and ethanol extracts of H. lydium against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, and 10 MRSA isolates was studied using the microdilution method. The effect of extracts with antibacterial activity on biofilm formation, hemolytic activity and catalase were also investigated by spectrophotometry-based methods. Finally, the effect of extracts on coagulase was determined by visually evaluating its effect on blood plasma coagulation. Results: The minimum inhibitory concentration (MIC) values of the ethanol extract were >1024 mu g.ml(-1) and 16 mu g.ml(-1) for E. coli and S. aureus standard strains, respectively. MRSA isolates were also inhibited at the same concentrations (16-32 mu g.ml(-1)) by the ethanol extract. On the other hand, the water extract did not show antibacterial activity (MIC value > 1024 mu g.ml(-1)) against any tested bacteria. Moreover, while the ethanol extract significantly inhibited biofilm formation and hemolytic activity, it had no effect on catalase and coagulase activity of selected MRSA isolates and S. aureus 29213. Conclusions: According to the results, the ethanol extract has the potential to be involved in drug formulations designed for the treatment of MRSA infections. In this context, further research about in-vivo efficacy and the level of toxicity needed.