Cloning and biochemical characterization of FOX-5, an AmpC-type plasmid-encoded beta-lactamase from a New York City Klebsiella pneumoniae clinical isolate.

Klebsiella pneumoniae 5064, isolated in New York, carried plasmid-mediated resistance to multiple beta-lactams and was unresponsive to clavulanic acid. The beta-lactamase gene responsible for cephalosporin resistance encoded FOX-5, with 96 to 97% amino acid identities to other members of the FOX family of beta-lactamases. The bla(FOX-5) coding region was located next to a transposase gene from the Aeromonas salmonicida insertion element ISAS2.