Effect of trans-Cinnamaldehyde on Adhesion and Other Virulence Factors of Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) produces virulence factors and causes hard-to-treat infections. This study aimed to evaluate the effect of trans-cinnamaldehyde (TC) on the selected virulence factors of MRSA: adhesion to host plasma and extracellular matrix proteins, protease, DNase and esterase production, and hemolytic activity. Our results showed that TC at ½ MBIC (Minimum Biofilm Inhibition Concentration) of 240 µg/mL or 60 µg/mL, depending on the isolate, significantly reduced MRSA adhesion. Inhibition varied between isolates, ranging from 26.1% to 41.3% (fibrinogen), 18.2% to 34.9% (elastin), 26.5% to 32.4% (laminin), and 17.1% to 30.5% (collagen). TC at ½ MIC (Minimum Inhibitory Concentration) of 30 µg/mL also significantly inhibited MRSA enzyme production, and reduced hemolytic activity (by 80.0–83.1%, depending on the isolate). TC may be an alternative to antibiotics for combating infections caused by S. aureus, as it not only reduces bacterial survival in the host but also reduces S. aureus virulence at subinhibitory concentrations. TC at higher concentrations exhibits cytotoxicity in human fibroblasts, limiting its topical use. Therefore, to exploit TC’s antibacterial potential, it is necessary to identify substances that act synergistically with it, enabling reduced effective doses.