Molecular Epidemiology and Characterization of Carbapenemase-Producing Enterobacteriaceae Isolated at a University Hospital in Korea during 4-Year Period

Abstract

Background : Carbapenemase-producing Enterobacteriaceae (CPE) has been increasingly reported worldwide in the past 10 years, which is an important infection control concern. Since the epidemiology and characteristics of these CPEs vary according to institutes, we aimed to characterize CPEs in a university hospital during the recent 4 years.

Methods : From October 2011 to September 2015, CPE isolates from clinical specimens and hospital surveillance cultures were collected. Carbapenem resistance was confirmed by disk diffusion method and Minimal Inhibitory Concentration (MIC) was determined by agar dilution method. Carbapenemase production was tested by double disk test using aminophenylboronic acid and dipicolic acid. PCR and sequence analysis were performed to detect blaKPC,blaIMP-1,blaVIM-2,blaNDM-1-like genes and blaOXA-48 gene. Pulsed-field gel electrophoresis (PFGE) and Multilocus sequence typing (MLST) were conducted for KPC-producing Klebsiella pneumoniae isolates.

Results : Twenty-five isolates (11%) of CPE were identified among 222 carbapenem-resistant Enterobacteriacae isolates during the study period. The most prevalent CPE was KPC-producing K. pneumonia and others were IMP-1, VIM-2, NDM-1 type and OXA-48 producing CPEs. Most of these CPEs showed resistance to carbapenems with variable MICs. The sequence types (STs) of KPC-producing K. pneumoniae were ST307 and ST11. The PFGE of ST11 and ST307 showed clonality in each group suggesting the possibility of in-hospital outbreak.

Conclusion : The prevalence of CPE has been increasing. In our institute, KPC-producing K. pneumoniae was the most frequently isolated CPE in the recent 4 years. CPE including KPC producers can easily transfer their resistance. Therefore continuous monitoring and more intensified infection control for CPE should be considered.