title: Role of OXA-23 and AdeABC efflux pump for acquiring carbapenem resistance in an Acinetobacter baumannii strain carrying the blaOXA-66 gene.
abstract: This study was performed to determine the mechanisms for acquiring carbapenem resistance in six clinical isolates of Acinetobacter baumannii. All isolates showed similar SmaI-macrorestriction patterns with less than 3 band differences by PFGE. The isolates showed a high level resistance (>32 mg/L) to both imipenem and meropenem by Etest. Phe-Arg-beta-naphthylamide lowered the MICs of carbapenems. Real-time PCR experiments showed that expression levels of the adeB gene in the six A. baumannii isolates were 10- to 40-times higher than those of imipenem-susceptible strains. Direct sequencing of PCR products showed that all isolates carried the bla(OXA-23) gene, which was preceded by ISAba1. The bla(OXA-23) probe hybridized with approximately 500-kb I-CeuI chromosomal fragments, but not with a plasmid. These findings suggest that overexpression of the AdeABC efflux pump as well as chromosome-borne OXA-23 may play a role in acquiring carbapenem resistance in our A. baumannii isolates.
authors.affiliation: Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yangsoon
authors.initials: Y
authors.lastname: Lee
authors.forename: Jong Hwa
authors.initials: JH
authors.lastname: Yum
authors.forename: Chang-Ki
authors.initials: CK
authors.lastname: Kim
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Jeon
authors.forename: Seok Hoon
authors.initials: SH
authors.lastname: Jeong
authors.forename: Jee Young
authors.initials: JY
authors.lastname: Ahn
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000368:Aged; D001426:Bacterial Proteins / Q000502:physiology*; D015153:Blotting, Western; D015780:Carbapenems / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D026901:Membrane Transport Proteins / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics / Q000502:physiology*
chemical_list: C492436:AdeA protein, Acinetobacter baumannii; C445684:AdeB protein, Acinetobacter baumannii; C492437:AdeC protein, Acinetobacter baumannii; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C466679:beta-lactamase OXA-23; D001618:beta-Lactamases