Integrated Experimental and Computational Discovery of Repurposed and Novel Inhibitors Targeting Staphylococcus aureus Biofilms.

BACKGROUND

Bacterial biofilms are highly resistant to antibiotics, leading to chronic infections. New approaches targeting biofilm formation (antivirulence) are urgently needed.

OBJECTIVES

To evaluate the antibiofilm efficacy of repurposed small-molecule drugs against Staphylococcus aureus and Pseudomonas aeruginosa, and to investigate their mechanisms of action via in vitro assays and in silico modeling.

METHODS

Twenty-nine compounds were screened for antibacterial activity (MIC) and for biofilm inhibition using microtiter plate assays. Seven lead compounds were identified and further tested for biofilm prevention and disruption. Computational studies included molecular docking of leads to key targets (e.g. P. aeruginosa LasR quorum-sensing receptor, S. aureus sortase A), 100 ns molecular dynamics simulations, and ADMET property prediction.

RESULTS

The lead compounds showed potent, dose-dependent inhibition of P. aeruginosa biofilm formation (approximately 49-87% at 250 µg/mL, and 71-100% at 500 µg/mL) without affecting planktonic growth (MIC >250 µg/mL). Two compounds (KAUS-31, KAUS-38) completely prevented P. aeruginosa biofilm formation at 500 µg/mL. Docking suggested high-affinity binding of the leads to LasR (GlideScores up to -12.6 vs -8.4 for native autoinducer), supporting a quorum-sensing inhibition mechanism. MD simulations indicated the lead-LasR complexes were less stable than the native ligand. All seven compounds showed drug-like profiles (no Lipinski rule violations), high predicted oral absorption, and no serious in silico toxicity flags.

CONCLUSION

Repurposed small molecules can serve as effective antibiofilm agents against S. aureus and P. aeruginosa. These compounds likely antagonize bacterial quorum sensing to suppress biofilms, while exhibiting favorable pharmacokinetic properties, highlighting a promising antivirulence strategy against biofilm-associated infections.