Molecular characterization of a transferable blaCTX-M-28 gene in clinical isolates of Enterobacter cloacae

The extended-spectrum beta-lactamase (ESBL) producing phenotype is frequent amongEnterobacter cloacae isolates at the Military Hospital of Tunis, Tunisia. We identified the ESBLs of a collection of these strains showing a particular extended-spectrum cephalosporin resistance profile characterized by a higher level of resistance to cefotaxime. These isolates were analyzed by antibiotic susceptibility testing, pI determination, plasmid profiles, transconjugation test, enterobacterial repetitive consensus (ERIC)-PCR and DNA sequencing. All these isolates were found to contain the CTX-M-28 ESBL genes and were multiresistant, producing other β-lactamases type of TEM-1 and OXA-1. ERIC-PCR analysis and conjugation experiments revealed that the dissemination of CTX-M-28 was due to both strain spreading and plasmid diffusion. The detection of CTX-M-28 on a conjugative plasmid is a significant factor for the dissemination of this enzyme. We supposed that the CTX-M-28-encoding plasmid will become an eventual epidemiological problem, by horizontal transfer, in ICU (Intensive Care Unit) of Military hospital in Tunisia.   Key words: β-lactamase, Enterobacter cloacae, cefotaximase, CTX-M-28, enterobacterial repetitive consensus (ERIC)-PCR