Characterization Of Carbapenemases, ESBLs Of Carbapenem-non-susceptible Enterobacter Cloacae

OBJECTIVE：To characterize the carbapenemases and ESBLs incarbapenem-non-susceptible (CNS) Enterobacter cloacae (E. cloacae)isolates from a Chinese teaching hospital，the First Affiliated Hospital ofChongqing Medical universitity.METHODS: A total of986non-duplicated E. cloacae isolatescollected between September2009and February2012were analyzed viaantimicrobial susceptibility testing. Carbapenemase and ESBL genes wereexamined using PCR amplification and DNA sequencing. Clonalrelatedness was investigated by pulsed-field gel electrophoresis (PFGE)and dendrogram analysis.RESULTS: CNSs were prevalent (35/986,3.55%) in E. cloacae.Phenotypes of carbapenemases and ESBLs were respectively found in9(25.7%) and23(65.7%) of the35CNS E. cloacae strains. KPC-2, IMP-8,IMP-26, NDM-1, TEM-6, CTX-M-3’, CTX-M-14’ and SHV-12typeβ-lactamases were identified in3(8.6%),5(14.3%),1(2.9%),1(2.9%),13(37.1%),9(25.7%),8(22.9%) and9(25.7%) isolates, respectively. Importantly, multiple resistance genes were found to be co-expressed in thesame CNS E. cloacae isolates. PFGE and dendrogram analysis showedclonal diversity among these isolates.CONCLUSION: Over-production of carbapenemases and ESBLscontributed together to the CNS of E. cloacae in China. Furthermore, thedecreased susceptibility to carbapenems in E. cloacae in the hospital mightarise via stepwise accumulations of multiple drug-resistance determinantsin different clones. The prevalence of CNS E. cloacae isolates was notcaused by clonal dissemination. Most importantly, we identified a CNS E.cloacae isolate co-expressing IMP-26and NDM-1, which is the firstreported to the best of our knowledge. This is also the first report ofNDM-1-producing Enterobacteriaceae in mainland China.