Repositioning of FDA-approved drugs for the treatment of methicillin-resistant Staphylococcus aureus infection: Structure-based virtual screening and in vitro assay

Background: Computer-aided repositioning of approved drugs is an increasingly popular strategy for the discovery of effective therapies. The potency of the newly repositioned drugs can be optimized using them as a component of an effective drug combination, thereby achieving the desired therapeutic effect at a lower and more tolerable drug concentration. Aim and Objectives: The aim of the study was to perform structure-based virtual screening and repurposing of FDA-approved drugs for the treatment of methicillin resistance by Staphylococcus aureus (SA) and perform an in vitro validation of the prediction. Materials and Methods: Following ethical clearance at the Department of Pharmacology and Therapeutics, College of Health Sciences, Usmanu Danfodiyo University Sokoto, molecular docking was performed against 5 validated protein targets involved in the development of methicillin resistance by SA and an in vitro validation of the prediction was done using 3 of the top-ranking drug candidates against methicillin-resistant vancomycin-susceptible strain of the pathogen (ATCC 43300). Results: Desmopressin and docetaxel, two of the 20 top-ranking repurposed drugs discovered through virtual screening, enhanced the inhibitory effect of oxacillin against the ATCC 43300 SA strain in a ratio-dependent manner, although each of the two drugs singly was only weakly effective against the bacterial strain. The standard drug, vancomycin (also among the top-scoring candidates), alone, was effective against ATCC 43300 strain and in combination with oxacillin, the two drugs produced a ratio-dependent synergistic effect against the bacterial strain. Conclusion: These findings suggest that oxacillin-based combinations with desmopressin, docetaxel, and the standard drug vancomycin, three of the 20 top-ranking drugs, at optimum ratios, may be beneficial in reversing the resistance of the ATCC 43300 SA strain to oxacillin, thus supporting the prediction of the molecular docking results.