title: Characterization of carbapenemases, extended spectrum β-lactamases and molecular epidemiology of carbapenem-non-susceptible Enterobacter cloacae in a Chinese hospital in Chongqing.
abstract: Carbapenem-resistant Enterobacteriaceae, including strains from multiple species harboring metallo-β-lactamases (IMP, NDM or VIM) and non-metallo (KPC) carbapenemases, as well as those combining an extended-spectrum β-lactamase (ESBL) enzyme with porin loss, present an increasingly urgent clinical danger. The aim of this study was to characterize the carbapenemases and ESBLs in carbapenem-non-susceptible (CNS) Enterobacter cloacae (E. cloacae) isolates from a Chinese teaching hospital. A total of 986 non-duplicated E. cloacae isolates collected between September 2009 and February 2012 were analyzed via antimicrobial susceptibility testing. Carbapenemase and ESBL genes were examined using PCR amplification and DNA sequencing. Clonal relatedness was investigated by pulsed-field gel electrophoresis (PFGE) and dendrogram analysis. We demonstrated that CNSs were prevalent (35/986, 3.55%) in E. cloacae. Phenotypes of carbapenemases and ESBLs were respectively found in 9 (25.7%) and 23 (65.7%) of the 35 CNS E. cloacae strains. KPC-2, IMP-8, IMP-26, NDM-1, TEM-6, CTX-M-3', CTX-M-14' and SHV-12 type β-lactamases were identified in 3 (8.6%), 5 (14.3%), 1 (2.9%), 1 (2.9%), 13 (37.1%), 9 (25.7%), 8 (22.9%) and 9 (25.7%) isolates, respectively. Importantly, multiple resistance genes were found to be co-expressed in the same CNS E. cloacae isolates. PFGE and dendrogram analysis showed clonal diversity among these isolates. Our study suggested that over-production of carbapenemases and ESBLs contributed together to the CNS of E. cloacae in China. Furthermore, the decreased susceptibility to carbapenems in E. cloaca in the hospital might arise via stepwise accumulations of multiple drug-resistance determinants in different clones. The prevalence of CNS E. cloacae isolates was not caused by clonal dissemination. Most importantly, we identified a CNS E. cloacae isolate co-expressing IMP-26 and NDM-1, which is the first reported to the best of our knowledge. This is also the first report of NDM-1-producing Enterobacteriaceae in mainland China.
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
authors.forename: Shan
authors.initials: S
authors.lastname: Sun
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.forename: Shifeng
authors.initials: S
authors.lastname: Huang
authors.forename: Xiaojiao
authors.initials: X
authors.lastname: Zhang
authors.forename: Liping
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology; D002681:China / Q000453:epidemiology; D016000:Cluster Analysis; D003428:Cross Infection; D016972:Enterobacter cloacae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D004756:Enterobacteriaceae Infections / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D055815:Young Adult; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D001618:beta-Lactamases; C063912:carbapenemase