Characterization of a Novel AmpC β-Lactamase Produced by a Carbapenem-Resistant Cedecea davisae Clinical Isolate

Abstract

ABSTRACTACedecea davisaeisolate, which was intermediate or resistant to third-generation cephalosporins and carbapenems, was recovered from a urine sample. Susceptibility testing, isoelectric focusing, and analysis of outer membrane proteins showed that AmpC β-lactamase expression combined with porin deficiency accounted for the carbapenem resistance. A cloning experiment followed by phenotypic and enzymatic characterization identified a novel class C enzyme that was phylogenetically and biochemically close to the chromosome-borne β-lactamases of the generaEnterobacterandCitrobacter.