ABSTRACTA meropenem-resistant Pseudomonas aeruginosaisolate was obtained from a patient in a medical setting in Hanoi, Vietnam. The isolate was found to have a novel IMP-type metallo-β-lactamase, IMP-51, which differed from IMP-7 by an amino acid substitution (Ser262Gly). Escherichia coliexpressing blaIMP-51showed greater resistance to cefoxitin, meropenem, and moxalactam than E. coliexpressing blaIMP-7. The amino acid residue at position 262 was located near the active site, proximal to the H263 Zn(II) ligand.