Pterostilbene restores carbapenem susceptibility in New Delhi metallo-β-lactamase-producing isolates by inhibiting the activity of New Delhi metallo-β-lactamases

Abstract

Background and Purpose: Bacteria producing New Delhi metallo-β-lactamase-1 (NDM-1) are an increasing clinical threat. NDM-1 can inactivate almost all β-lactams and is not sensitive to any existing β-lactamase inhibitors. To identify effective inhibitors of the NDM-1 enzyme and clarify the mechanism of action, a “lead compound” for developing more potent NDM-1 inhibitors needs to be provided. Experimental Approach: Natural compounds were tested by enzyme inhibition screening to find potential inhibitors. MIC assays, growth curve assays, and time-kill assays were conducted to evaluate the in vitro antibacterial activity of pterostilbene and the combination of pterostilbene and meropenem. A murine thigh model and a mouse pneumonia model were used to evaluate the in vivo efficacy of combined therapy. Molecular modelling and a mutational analysis were used to clarify the mechanism of action. Key Results: Pterostilbene significantly inhibited NDM-1 hydrolysis activity in enzyme inhibition screening assays and effectively restored the effectiveness of meropenem in vitro with NDM-expressing isolates in antibacterial activity assays. In addition, the combined therapy effectively reduced the bacterial burden in a murine thigh model and protected mice from pneumonia caused by Klebsiella pneumoniae. By means of molecular dynamics simulation, we observed that pterostilbene localized to the catalytic pocket of NDM-1, hindering substrate binding to NDM-1 and reducing NDM-1 activity. Conclusions and Implications: These findings indicated that pterostilbene combined with meropenem may offer a new safe and potential “lead compound” for the further development of NDM-1 inhibitors.