title: Combination of IMP-4 metallo-beta-lactamase production and porin deficiency causes carbapenem resistance in a Klebsiella oxytoca clinical isolate.
abstract: This study shows for the first time the mechanism of carbapenem resistance of a Klebsiella oxytoca clinical isolate ZC101 recovered from a Zhejiang University Hospital in Hangzhou, China. MIC values of imipenem, meropenem, and ertapenem for K. oxytoca ZC101 were 16, 16, and 128 microg/mL, respectively. Conjugation experiments demonstrated the transferability of a resistance determinant from K. oxytoca ZC101 to Escherichia coli EC600. Results from isoelectric focusing, polymerase chain reactions, and DNA sequencing confirmed that K. oxytoca ZC101 produced IMP-4 metallo-beta-lactamase (MBL) and CTX-M-14 extended-spectrum beta-lactamase, whereas E. coli transconjugant only produced the IMP-4. Amplification of integron revealed that bla(IMP-4) gene is located within a class I integron that was carried in a plasmid approximately 55 kb in size. Sodium dodecyl sulfate polyacrylamide gel electrophoresis profiling of outer membrane proteins of K. oxytoca ZC101 indicated lack of expression of the OmpK36 porin. DNA sequence analysis of ompK36 gene of K. oxytoca ZC101 showed the gene was disrupted by an insertion sequence IS5. In all, the results show that plasmid-mediated IMP-4 MBL production combined with the loss of OmpK36 porin caused the resistance in K. oxytoca ZC101 to carbapenems.
authors.affiliation: Second Affiliated Hospital of Zhejiang University, Zhejiang University, Hangzhou 310009, China.
authors.forename: Li-Rong
authors.initials: LR
authors.lastname: Chen
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Zhou
authors.forename: Jia-Chang
authors.initials: JC
authors.lastname: Cai
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Gong-Xiang
authors.initials: GX
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis; D015780:Carbapenems / Q000494:pharmacology*; D002681:China; D003227:Conjugation, Genetic; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D022761:Gene Transfer, Horizontal; D006761:Hospitals; D006801:Humans; D007525:Isoelectric Focusing; D007710:Klebsiella Infections / Q000382:microbiology; D041121:Klebsiella oxytoca / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000032:analysis; D018272:Porins / Q000172:deficiency*; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D018272:Porins; C425142:beta-lactamase IMP-4; C000595277:IMP-4 beta-lactamase, Klebsiella oxytoca; D001618:beta-Lactamases