Covalent inhibition of New Delhi metallo-β-lactamases NDM-1 and NDM-5 by 3-bromopyruvate.

OBJECTIVES: Resistance to β-lactam antibiotics, including carbapenems, mediated by metallo-β-lactamases (MBLs), including the New Delhi metallo-β-lactamase (NDM) family, is increasing. No MBL inhibitors are currently approved for clinical use, with most reported MBL inhibitors acting as metal ion chelators at either the Zn(II) ion active site and/or in solution. The hexokinase inhibitor 3-bromopyruvate (3-BP) has been reported to inhibit NDM-1. This study investigates the ability of 3-BP to restore carbapenem activity against NDM-producing bacterial strains. MATERIALS AND METHODS: The ability of 3-BP to restore meropenem activity was assessed against carbapenem-resistant Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii strains, obtained from clinical and environmental isolates from Tanzania and Malawi. The mechanism of inhibition was investigated using mass spectrometry studies with both biologically relevant sulphur-containing compounds in addition to NDM-1 and NDM-5. RESULTS AND CONCLUSIONS: 3-BP selectively restored the antimicrobial activity of meropenem against resistant strains containing genes encoding NDM-1 or NDM-5 but did not restore the antimicrobial activity of amoxicillin against resistant strains containing genes encoding serine β-lactamases. Mass spectrometry studies with NDM-1 and NDM-5 support a mechanism involving covalent reaction of 3-BP with an active site cysteine residue. These results will promote work on the development of covalently reacting MBL inhibitors, a strategy that has been successful for inhibition of the nucleophilic serine β-lactamases.