Repurposing trifluridine as an anti-Staphylococcus aureus agent targeting virulence factor staphyloxanthin and attachment genes.

This work explores the antibacterial and antibiofilm activities of trifluridine (TRFD) against S. aureus. The Minimum Inhibitory Concentrations (MIC) and Minimum Biofilm Inhibitory Concentrations (MBIC50) for TRFD were observed at 1.562 mg L-1 and 1 mg L-1 for ciprofloxacin-susceptible S. aureus (CSSA) and at 0.0625 mg L-1 and 0.14 mg L-1 for ciprofloxacin-resistant S. aureus (CRSA). Synergistic and partial synergistic antimicrobial effects of TRFD combined with ciprofloxacin (CIP) were observed against CSSA and CRSA, respectively, along with synergistic and indifferent antibiofilm effects. The TRFD + CIP significantly increased plasma membrane damage and generated ROS, affecting staphyloxanthin production, partially reducing slime production, and inhibiting the cell surface hydrophobicity and pellicle production. TRFD + CIP also reduced the carbohydrate and eDNA contents of extracellular polymeric substances. TRFD + CIP treatment decreased icaR, fnbA, and clfB expression and increased icaA, efb, and map expression. Scanning electron microscopy analysis revealed the TRFD + CIP-treated S. aureus biofilm and planktonic cells with deformities and debris.