Reduced imipenem susceptibility in Klebsiella pneumoniae clinical isolates with plasmid-mediated CMY-2 and DHA-1 β-lactamases co-mediated by porin loss

Kyungwon Lee, Dongeun Yong, Yeong Seon Choi, Jong Hwa Yum, June Myung Kim, Neil Woodford, David M. Livermore, Yunsop Chong

Research output: Contribution to journalArticle

51 Citations (Scopus)


We investigated the resistance mechanisms and clonality among 42 imipenem-non-susceptible Klebsiella pneumoniae isolated at a tertiary care hospital in Korea. Two isolates had blaVIM-2 alleles, whereas blaCMY-2- and blaDHA-1-like alleles were detected in 24 and 16 isolates, respectively, with these enzymes confirmed by sequencing for representative isolates. Transfer of blaCMY-2 and blaDHA-1 was achieved by conjugation. Addition of 300 mg/L 3-aminophenylboronic acid (APB) reduced the minimum inhibitory concentration for 90% of the organisms (MIC90) of imipenem and meropenem eight- and four-fold, respectively, for the blaCMY-2- and blaDHA-1-positive isolates, confirming the role of these enzymes in resistance. SDS-PAGE of outer membrane proteins for representative isolates showed lack or greatly diminished expression of OmpK35 and OmpK36 porins. Pulsed-field gel electrophoresis of XbaI-restricted genomic DNA revealed two closely related clusters among 23 blaCMY-2-positive isolates, whereas those with blaDHA-1 were more heterogeneous. In conclusion, reduced imipenem susceptibility among K. pneumoniae at this Korean hospital was largely co-mediated by production of plasmid-mediated AmpC β-lactamases along with lack or greatly diminished expression of OmpK35 and OmpK36 porins.

Original languageEnglish
Pages (from-to)201-206
Number of pages6
JournalInternational Journal of Antimicrobial Agents
Issue number2
Publication statusPublished - 2007 Feb 1


All Science Journal Classification (ASJC) codes

  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)

Cite this