Identification of Potential AcrAB-TolC Efflux Pump Inhibitors in Escherichia coli using an Ethidium Bromide Method.

Many bacteria are known to exhibit antibiotic resistance through overexpression of efflux pumps. In this experiment, inhibition of a bacterial efflux pump through the physical binding of small molecule inhibitor compounds was explored as a way to combat substrate expulsion. The TolC protomer of the AcrAB-TolC efflux pump in Escherichia coli was targeted in a virtual screen for novel small molecule inhibitor compounds. PyRx AutoDock Vina was used to virtually dock the various small molecules to the TolC protein and rank the compounds based on favorable binding energies. Five lead-compounds from the virtual screen were ultimately selected for in vivo efflux testing with and without prolonged incubation of the bacterial cells with the test compounds. Efflux activity was monitored using an ethidium bromide substrate to determine the relative extent of inhibition. Results showed little to no effect on efflux activity unless the bacterial cells were cultured with the test compound for an overnight incubation. Bacteria with prolonged compound incubation displayed significantly decreased efflux activity for several small molecule compounds that were tested. These findings suggest that efflux pump inhibition should be focused mainly on halting underlying synthesis and assembly mechanisms rather than hindering the functionality of the pump.https://ecommons.udayton.edu/stander_posters/1723/thumbnail.jp