title: Reduced susceptibility to carbapenems in Klebsiella pneumoniae clinical isolates associated with plasmid-mediated beta-lactamase production and OmpK36 porin deficiency.
abstract: Two carbapenem-non-susceptible Klebsiella pneumoniae isolates, Z2554 and Z2110, were collected from a hospital in China and analysed by PFGE. K. pneumoniae Z2554 and Z2110 were genetically unrelated and showed resistance to ertapenem, and reduced susceptibility to imipenem and meropenem. Analysis of their beta-lactamases indicated that K. pneumoniae Z2554 produced TEM-1 and CTX-M-14 beta-lactamases, whilst Z2110 produced a plasmid-mediated AmpC beta-lactamase, DHA-1, in addition to TEM-1 and CTX-M-14. SDS-PAGE analysis of the outer-membrane proteins (OMPs) revealed that both isolates lacked an OMP of approximately 39 kDa (OmpK36), whilst Z2110 had an additional protein with an approximate molecular mass of 26 kDa. Analysis of the OMP-encoding genes demonstrated that the ompK35 sequence of K. pneumoniae Z2554 and Z2110 contained a number of silent mutations. In ompK36, several insertions and deletions of short DNA fragments (1-6 bp) were detected in both isolates. The N-terminal sequence of the approximately 26 kDa protein band identified in Z2110 had no similarity to the sequence of OmpK36. Instead, it shared high similarity with hypothetical protein KPN_03267 originating from K. pneumoniae subsp. pneumoniae MGH 78578. It was concluded that beta-lactamase production combined with OmpK36 deficiency results in ertapenem resistance, and reduced imipenem and meropenem susceptibility, in K. pneumoniae Z2554 and Z2110. OmpK36 may play an important role in the resistance or reduced susceptibility to carbapenems in K. pneumoniae producing AmpC, extended-spectrum beta-lactamase or broad-spectrum beta-lactamase.
authors.affiliation: 2nd Affiliated Hospital of Zhejiang University, Zhejiang University, 88 Jiefang Road, Hangzhou 310009, PR China.
authors.forename: Xuan Ding
authors.initials: XD
authors.lastname: Wang
authors.affiliation: 2nd Affiliated Hospital of Zhejiang University, Zhejiang University, 88 Jiefang Road, Hangzhou 310009, PR China.
authors.forename: Jia Chang
authors.initials: JC
authors.lastname: Cai
authors.affiliation: 2nd Affiliated Hospital of Zhejiang University, Zhejiang University, 88 Jiefang Road, Hangzhou 310009, PR China.
authors.forename: Hong Wei
authors.initials: HW
authors.lastname: Zhou
authors.affiliation: 2nd Affiliated Hospital of Zhejiang University, Zhejiang University, 88 Jiefang Road, Hangzhou 310009, PR China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: 2nd Affiliated Hospital of Zhejiang University, Zhejiang University, 88 Jiefang Road, Hangzhou 310009, PR China.
authors.forename: Gong-Xiang
authors.initials: GX
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015780:Carbapenems / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D022761:Gene Transfer, Horizontal; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism*; D018272:Porins / Q000235:genetics / Q000378:metabolism*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; C092233:OmpK36 protein, Klebsiella pneumoniae; D018272:Porins; D001618:beta-Lactamases