Occurrence of extended-spectrum β-lactamases among chromosomal AmpC-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens in Korea and investigation of screening criteria

Yeon Joon Park, Sun Young Park, Eun Jee Oh, Jung Jun Park, Kyo Young Lee, Gun Jo Woo, Kyungwon Lee

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We assessed the occurrence and screening criterion for extended-spectrum β-lactamases (ESBLs) among AmpC-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens. The 413 isolates (158 E. cloacae, 126 C. freundii, and 129 S. marcescens) isolated from 11 clinical laboratories in Korea were investigated. ESBL production was confirmed by double-disk synergy test and inhibitor-potentiated diffusion test using ceftazidime (CAZ), cefotaxime (CTX), aztreonam (AZT), and cefepime (FEP) with or without clavulanic acid. One hundred seven isolates (25.9%) were as ESBL producers. Of them, resistance was transferred by conjugation in 82 isolates. In transconjugants, structural genes for CTX-M (53.7%), TEM (46.3%), SHV (29.3%) were found. To evaluate the ESBL screening minimum inhibitory concentration (MIC) criteria, MICs for cefuroxime, CAZ, CTX, AZT, and FEP were determined and cutoff value was selected using receiver operator characteristic curve. The FEP MIC ≥ 1 μg/mL had the highest sensitivity (95.3%), specificity (82.7%), and positive (65.8%) and negative predictive values (98.3%).

Original languageEnglish
Pages (from-to)265-269
Number of pages5
JournalDiagnostic Microbiology and Infectious Disease
Issue number4
Publication statusPublished - 2005 Apr


All Science Journal Classification (ASJC) codes

  • Microbiology (medical)
  • Infectious Diseases

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