KHM-1, a Novel Plasmid-Mediated Metallo-β-Lactamase from a Citrobacter freundii Clinical Isolate

A novel gene, bla KHM-1 , encoding a metallo-β-lactamase, KHM-1, was cloned from a clinical isolate of Citrobacter freundii resistant to most β-lactam antibiotics. Escherichia coli expressing bla KHM-1 was resistant to all broad-spectrum β-lactams except for monobactams and showed reduced susceptibility to carbapenems. Recombinant KHM-1 exhibited EDTA-inhibitable hydrolytic activity against most β-lactams, with an overall preference for cephalosporins.