Repurposing GSK2018682 Confers Dual Antibacterial and Antibiofilm Activity against Staphylococcus aureus

The increase in the level of antibiotic-resistant Staphylococcus aureus underscores the urgent need for novel therapeutics. Consequently, repurposing clinically approved drugs has emerged as a compelling and time-saving strategy to counteract this escalating antimicrobial crisis. Here, high-throughput screening revealed that GSK2018682, an agonist of sphingosine-1-phosphate receptors S1P1 and S1P5, exhibits potent, broad-spectrum antimicrobial activity, particularly against S. aureus (MIC = 25-50 μM) and E. faecalis (MIC = 12.5-25 μM). GSK2018682 exhibited concentration-dependent bactericidal activity against both MSSA and MRSA, eradicating planktonic S. aureus within 6 h at 4× MIC. At sub-MIC concentrations, GSK2018682 significantly inhibited biofilm formation, and at 4× MIC, it killed the bacterial cells embedded in mature biofilms. Proteomics revealed that GSK2018682 caused global expression perturbations of functional proteins involved in a two-component system, various metabolic pathways, ribosomal functions, and biofilm regulatory factors (e.g., pflB, sarA). Drug Affinity Responsive Target Stability (DARTS) experiments implicated icaB (a PNAG deacetylase) and phospholipid synthase SAOUHSC_01260 as its candidate targets. Furthermore, GSK2018682 could increase membrane permeability, depolarize, and enhance fluidity to disrupt the S. aureus membranes. Exogenous phospholipid supplementation markedly attenuated the antibacterial efficacy of GSK2018682 against S. aureus. Finally, GSK2018682 displayed a strong efficacy in murine models of MRSA infection. In summary, our findings establish GSK2018682 as a promising anti-S. aureus agent with dual antibacterial and antibiofilm activities, acting through interaction with membrane phospholipids to disrupt membrane integrity and offering a strategy against resistant S. aureus infections.