Infections caused by naturally AmpC-producing Enterobacteriaceae: can we use third generation cephalosporins? A narrative review

Abstract The burden of antibiotic-resistant infections among Gram negative bacteria is increasing. Resistance to third generation cephalosporins (3GC) in Enterobacteriaceae is mainly conferred by beta-lactamases acquisition or deregulation of the natural genetically encoded enzyme. Enterobacteriaceae such as Enterobacter spp., Serratia marcescens, Citrobacter freundii, Providencia spp. and Morganella morganii (ESCPM group) possess chromosomally encoded inducible AmpC beta-lactamases. AmpC can be overproduced as a response to beta-lactam antibiotics exposure or from a constitutive dysfunction of the AmpC regulation system. This overproduction can lead to the inactivation of 3GC. Based on small-sized clinical studies, international guidelines and expert recommendations suggest that 3GC should be avoided as definitive therapy for infections caused by ESCPM group. In this narrative review, we will discuss the published literature and evaluate the risk related to 3GC use in case of documented ESCPM infection.