Extended-spectrum cephalosporinases: structure, detection and epidemiology

Extended-spectrum AmpC beta-lactamases of Enterobacteriaceae, which are chromosomally or plasmid-encoded, possess structural modifications in the vicinity of the active site compared with their progenitors. They display an increased catalytic efficiency against extended-spectrum beta-lactams, such as ceffazidime, cefotaxime, cefepime, cefpirome and, in some cases, also against imipenem. An overview of the molecular and biochemical characterization of this recently identified mechanism of resistance to beta-lactams is provided as well as its prevalence and possible clinical significance.