An outbreak of carbapenem-resistant enterobacter cloacae in pediatric intensive care unit of a Chinese teaching hospital

Objective: Carbapenem-resistant Enterobacter cloacae infections are known to be particularly prevalent in vulnerable populations, especially children. However, the phenotypic and molecular characteristics of carbapenemresistant E. cloacae infections in the pediatric wards of China have not been well described. The aim of the present study was to characterize an outbreak of carbapenem-resistant E. cloacae in a pediatric intensive care unit of a teaching hospital. Methods: A total of 10 non-duplicated carbapenem-resistant E. cloacae from pediatric patients were collected and analyzed by antimicrobial susceptibility testing. The Modified Hodge test (MHT) was used for the preliminary screening of carbapenemases. β-lactamase genes were examined by PCR for sequencing. The transferability of the carbapenemase genes and the homology of the 10 strains were evaluated by a conjugation experiment and pulsed-field gel electrophoresis (PFGE), respectively. Results: The results showed that all of the 10 isolates exhibited carbapenemase activity and carried carbapenemase genes. The Klebsiella pneumoniae carbapenemase (blaKPC-2) genes were detected in 6 of the 10 isolates, the blaIMP-8 metallo-β-lactamase gene was detected in 1 isolate. Interestingly, the New Delhi metallo-β-lactamase (blaNDM-1) gene, which is rarely found in children, was identified in 3 isolates. Further, extended spectrum beta-lactamases (ESBLs) and cephalosporinases (AmpC enzyme) genes were detected in the majority of the carbapenem-resistant E. cloacae isolates. All carbapenemase genes were located on transferable plasmids. PFGE demonstrated that 10 carbapenemase-producing E. cloacae isolates had homology and that there were five different clone patterns. Conclusions: Our study indicated that carbapenemase-production was the main contributor to this nosocomial infection outbreak because of the E. cloacae found in the pediatric intensive care unit.