First report of CTX-M-9 in a clinical isolate of Enterobacter cloacae in a Tunisian hospita

β-lactamases are one of several mechanisms of bacterial resistance to β-lactam antibiotics. The aim of this study was to analyze the resistance to extended-spectrum cephalosporins of a multidrug-resistant isolate of Enterobacter cloacae, BF5011. This strain was isolated from a stool culture, during the nosocomials infections occurring in the intensive care unit of the Military Hospital of Tunis in 2005. Analysis of E. cloacae BF5011 by double-disk synergy test yielded a positive result suggesting the production of extended-spectrum-β-lactamases. Cell sonicate of this isolate is very active against cefotaxime and showed a specific activity (AS) of 7,54 U/mg for the same antibiotic. This activity was inhibited by the sulbactam and the clavulanic acid. By polymerase chain reaction and sequencing, the isolate was found to produce extended-spectrum-β-lactamase, CTX-M-9. The bla CTX-M-9 gene was transferred from E. cloacae by conjugation. Isoelectric focusing method revealed one band with a pI of about 8. This is the first report of CTX-M-9 in Tunisia. © 2009 Elsevier Masson SAS.