Evaluating the Efficacy of Drug Efflux Pump Inhibitors Through Growth Curve Analysis

Drug efflux pumps are ubiquitous in bacterial genomes, and it has been shown that each bacterium harbors multiple of them. These pumps play crucial roles not only in drug resistance but also in pathogenicity, virulence, biofilm formation, and resistance to metabolic products. Therefore, they represent promising targets for the development of new drugs and efflux pump inhibitors aimed at combating bacterial infections by suppressing multiple key functions. Despite ongoing research efforts, clinically effective inhibitors remain elusive, which has prompted research and development involving large-scale compound screening in various research groups. However, to evaluate the inhibitory activity of candidate compounds, Minimum Inhibitory Concentration (MIC) assays are often unsuitable, as they require substantial quantities of compounds that may be rare or expensive. To address this, this chapter describes a method for conveniently evaluating the pump-inhibitory activity of multiple inhibitor substances at different concentrations using growth curve measurements, which require only small amounts of compounds.