Evaluating the ciprofloxacin potentiation efficacy of repurposed drug flupentixol through efflux pump inhibition of pathogenic bacteria.

Antimicrobial resistance concerning burdens is increasing day by day. Efflux pump upregulation is one of the mechanisms through which bacteria develop resistance to antibiotics. To overcome this escalating problem in healthcare, repurposing existing drugs as efflux pump inhibitors in combination with antibiotics can help mitigate the growing resistance issue worldwide. In our study, we investigated the efflux pump inhibiting capability of the repurposed drug flupentixol in combination with different classes of antibiotics. In vitro combination susceptibility testing (disk diffusion and minimum inhibitory concentration-MIC), in vivo shigellosis mouse model, and in silico study (molecular docking and simulation) were investigated. Ciprofloxacin-flupentixol yield promising in vitro results against Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 25,923, and Shigella boydii AL 17,313. The clinical efficacy of ciprofloxacin-flupentixol was evaluated in the shigellosis mouse model. Clinical parameters, including percentage changes in body weight, total white blood cell (WBC) count, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR), were evaluated. In vivo findings supported the use of this combination in reducing the body's inflammatory state. Molecular docking and simulation study targeted the efflux pump proteins NorA (PDB ID: 7LO8), MexA Protein (PDB ID: 6IOK), and AcrB (PDB ID: 4CDI), to investigate the efflux pump inhibiting capability of flupentixol. Molecular dynamics simulations confirmed the stability of the protein-flupentixol complex over 100 ns, supporting that flupentixol synergizes with ciprofloxacin by inhibiting the NorA efflux pump.