Studying the Anti-Virulence Activity of Meta-Bromo-Thiolactone against Staphylococcus aureus and MRSA Phenotypes

Quorum-sensing inhibitors have recently garnered great interest, as they reduce bacterial virulence, lower the probability of resistance, and inhibit infections. In this work, meta-bromo-thiolactone (mBTL), a potent quorum and virulence inhibitor of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA), was formulated in chitosan nanoparticles (ChNPs) using the ionic gelation method. The mBTL-loaded-ChNPs were characterized by their particle size, polydispersity index, zeta potential, morphology, and drug release profile. The results show that the mBTL-loaded-CNPs comprised homogenized, spherical nanoparticles ranging from 158 ± 1.3 to 284 ± 5.6 nm with a sustainable release profile over 48 h at 37 °C. These findings confirm the successful preparation of mBTL-loaded-ChNPs. Confocal laser scanning microscopy showed a significant reduction in the number of viable cells, indicating the antibacterial efficacy of mBTL. Biofilms were observed by scanning electron microscopy, which showed that the bacterial cells in the control experiment were enclosed in thick biofilms. In the presence of mBTL, the bacterial cells remained disordered and did not form a biofilm. mBTL-loaded-ChNPs represent a potential approach to overcoming antimicrobial resistance in the treatment of MRSA infection.