Hospital-acquired infections are a significant concern in healthcare facilities. Staphylococcus aureus (commonly known as “Golden staph”), is a major cause of these infections, and can often be linked to inadequate disinfection of surfaces and medical equipment. Such infections are potentially increasing in frequency as the problem is exacerbated due to a rise in bacterial resistance to disinfectants. One of the key mechanisms of bacterial antimicrobial resistance are multidrug efflux pumps, proteins that pump multiple compounds out of the cell. Staphylococci possess many efflux pumps, where QacA is the major contributor to resistance to antiseptic and disinfectants. Therefore, deactivation of these pumps would increase the effectiveness of existing antimicrobials.
The overarching objective of this work is to identify QacA inhibitors by designing a bespoke virtual screening pipeline and subsequent biological assays. Molecular docking studies usually rely on docking results without validating software suitability. Here, we initially tested a set of compounds for their ability to inhibit QacA using an improved transport inhibition assay. The results were used to validate several virtual docking tools. The most effective tool was used to screen a library of thousands of compounds. The top-scored compounds were grouped based on physiochemical similarities, and a selection was made across these groups for transport inhibition assay. From that, two compounds were identified that significantly inhibit QacA, both come from distint and novel chemical scaffolds. Further investigation into compounds of related scaffolds confirmed additional inhibitors. Our further analysis also indicates that the use of these efflux pump inhibitors can enhance the efficacy of disinfectants under clinically relevant conditions, suggesting potential clinical applications. This research represents a robust appoarch to identify inhibitors for multidrug efflux pump in general, which can potentially reverse antimicrobial resistance and reducing hospital-acquired infections.