title: Mechanism of imipenem resistance acquired by three Pseudomonas aeruginosa strains during imipenem therapy.
abstract: Imipenem sensitive pretherapy isolates (MICs 1-2 mg/l) and the corresponding resistant posttherapy isolates (MICs 16 mg/l) of Pseudomonas aeruginosa from three patients undergoing imipenem treatment were analyzed to establish the resistance mechanism. The identity of pyocin types, serotypes, DNA restriction endonuclease profiles and plasmid profiles strongly suggested isogenicity of pre- and posttherapy isolates. The imipenem resistant posttherapy isolates showed cross-resistance only to another carbapenem, meropenem. There were neither qualitative nor quantitative differences between pre- and posttherapy isolates in beta-lactamase production. Affinity of the penicillin-binding proteins 1A, 1B, 2, 3, 4,4' and 5 for [14C]imipenem was the same in pre- and posttherapy isolates. One-dimensional and two-dimensional gel electrophoresis of outer membrane protein preparations showed diminished expression of an outer membrane protein of about 46.5 and 47.5 kilodaltons, respectively, in the posttherapy isolates. This protein had an apparent isoelectric point of about pH 5.2 in two-dimensional gel electrophoresis. Growth in proteose peptone no. 2 broth did not reduce expression of this outer membrane protein, which spoke against its identity with the outer membrane protein D1. The permeability of the outer membrane for imipenem was reduced in the posttherapy isolates, since addition of 0.5 or 0.25 of the MIC of the permeabilizing agent ethylene-diaminetetraacetate reduced the MICs of imipenem for all isolates from each patient to the same (susceptible) level. The diminished expression of one of the outer membrane proteins might be the reason for this reduced permeability.
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Vurma-Rapp
authors.forename: F H
authors.initials: FH
authors.lastname: Kayser
authors.forename: K
authors.initials: K
authors.lastname: Hadorn
authors.forename: F
authors.initials: F
authors.lastname: Wiederkehr
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D001426:Bacterial Proteins; D015373:Bacterial Typing Techniques; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000032:analysis; D004352:Drug Resistance, Microbial; D004492:Edetic Acid / Q000494:pharmacology; D006602:Hexosyltransferases; D006801:Humans; D015378:Imipenem / Q000494:pharmacology* / Q000627:therapeutic use; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D011552:Pseudomonas Infections / Q000188:drug therapy* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects* / Q000201:enzymology; D012703:Serotyping; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D015378:Imipenem; D004492:Edetic Acid; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D001618:beta-Lactamases