Novel metallo-ß-lactamases inhibitors restore the susceptibility of carbapenems to New Delhi metallo-lactamase-1 (NDM-1)-harbouring bacteria

Background and purpose: The production of metallo-ss-lactamases is a major mechanisms adopted by bacterial pathogens to resist carbapenems. Repurposing approved drugs to restore the efficacy of carbapenems represents an efficient and costeffective approach to fight infections caused by carbapenem resistant pathogens. Experimental approach: The nitrocefin hydrolysis assay was employed to screen potential New Delhi metallo-lactamase-1 (NDM-1) inhibitors from a commercially available U.S. Food and Drug Administration (FDA) approved drug library. The mechanism of inhibition was clarified by metal restoration, inductively coupled plasma mass spectrometry (ICP-MS) and molecular dynamics simulation. The in vitro synergistic antibacterial effect of the identified inhibitors with meropenem was determined by the checkerboard minimum inhibitory concentration (MIC) assay, time-dependent killing assay and combined disc test. Three mouse infection models were used to further evaluate the in vivo therapeutic efficacy of combined therapy. Key results: Twelve FDA-approved compounds were initially screened to inhibit the ability of NDM-1 to hydrolyse nitrocefin. Among these compounds, dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid were demonstrated to inhibit all tested metallo-ss-lactamases and showed an in vitro synergistic bactericidal effect with meropenem against metallo-ss-lactamases-producing bacteria. Dexrazoxane, embelin and candesartan cilexetil are metal ion chelating agents, while the inhibition of NDM-1 by nordihydroguaiaretic acid involves its direct binding to the active region of NDM-1. Furthermore, these four drugs dramatically rescued the treatment efficacy of meropenem in three infection models. Conclusions and implications: Our observations indicated that dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid are promising carbapenem adjuvants against metallo-ss-lactamases-positive carbapenem resistant bacterial pathogens.