AmpC β-lactamase in an Escherichia coli clinical isolate confers resistance to expanded-spectrum cephalosporins

Cloning, sequencing, and biochemical analysis identified a novel AmpC-type beta-lactamase conferring resistance to extended-spectrum cephalosporins in an Escherichia coli clinical isolate. This enzyme, exhibiting 14 amino acid substitutions compared to a reference AmpC cephallosporinase of E. coli, hydrolyzed ceftazidime and cefepime significantly.