Design of New Antibacterial Enhancers Based on AcrB’s Structure and the Evaluation of Their Antibacterial Enhancement Activity

Previously, artesunate (AS) and dihydroartemisinine 7 (DHA7) were found to have antibacterial enhancement activity againstEscherichia colivia inhibition of the efflux pump AcrB. However, they were only effective againstE. colistandard strains. This study aimed to develop effective antibacterial enhancers based on the previous work. Our results demonstrate that 86 new antibacterial enhancers were designed via 3D-SAR and molecular docking. Among them, DHA27 had the best antibacterial enhancement activity. It could potentiate the antibacterial effects of ampicillin against not onlyE. colistandard strain but also clinical strains, and of β-lactam antibiotics, not non-β-lactamantibiotics. DHA27 could increase the accumulation of daunomycin and nile red withinE. coliATCC 35218, but did not increase the bacterial membrane permeability. DHA27 reducedacrB’s mRNA expression ofE. coliATCC 35218 in a dose-dependent manner, and its antibacterial enhancement activity is related to the degree ofacrBmRNA expression inE. coliclinical strains. The polypeptides from AcrB were obtained via molecular docking assay; the pre-incubated polypeptides could inhibit the activity of DHA27. Importantly, DHA27 had no cytotoxicity on cell proliferation. In conclusion, among newly designed antibacterial enhancers, DHA27 had favorable physical and pharmacological properties with no significant cytotoxicity at effective concentrations, and might serve as a potential efflux pump inhibitor in the future.Keywords:antibacterial enhancer;AcrB inhibitor;DHA27;molecular mechanism