Full Paper Phenotypic and molecular characterization of a novel β-lactamase carried by Klebsiella pneumoniae, CTX-M-72, derived from CTX-M-3

Resistance to the expanded-spectrum cephalosporins has become a worldwide problem. Such resistance occurs primarily in members of the family Enterobacteriaceae via the production of extendedspectrum β-lactamases (ESBLs), which are capable of hydrolyzing the oxyimino-cephalosporins and monobactams (Bush et al., 2001; Pitout et al., 2004). It has recently been shown that the CTX-M β-lactamases are a group of molecular class A ESBLs that exhibit their powerful spectrum of hydrolysis of cefotaxime, but have only marginal effects on the MIC of ceftazidime. The blaCTX-M genes are predominatly present on transferable plasmids (Tzouvelekis et al., 2000); thus, the CTX-M β-lactamases-producing strains are enJ. Gen. Appl. Microbiol., 55, 207‒216 (2009)