title: Mechanisms of resistance to beta-lactam antibiotics in Acinetobacter calcoaceticus.
abstract: Examination of 12 strains of Acinetobacter calcoaceticus revealed that the strains expressed different constitutive levels of beta-lactamase. Mutants resistant to cefoxitin, cefoperazone or ceftazidime were selected from a strain producing a low level of beta-lactamase. All the mutants showed no change in expression of beta-lactamase, but produced penicillin-binding proteins with altered expression and/or affinity for beta-lactams. In addition, the outer membrane of the mutants showed decreased permeability (40-80% that of the parent strain) towards small hydrophilic solutes, together with diminished production of a 46.5 kDa porin protein. It was concluded that the enhanced resistance to beta-lactams in the A. calcoaceticus mutants was the result of interplay between the altered penicillin binding proteins and the reduced outer membrane permeability.
authors.affiliation: Department of Cellular Information Sciences, Tokai University School of Medicine, Isehara, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Obara
authors.forename: T
authors.initials: T
authors.lastname: Nakae
mesh_terms: D016954:Acinetobacter calcoaceticus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism; D002463:Cell Membrane Permeability; D004352:Drug Resistance, Microbial; D006602:Hexosyltransferases; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism; D010458:Peptidyl Transferases; D001618:beta-Lactamases / Q000032:analysis / Q000378:metabolism; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D047090:beta-Lactams; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D001618:beta-Lactamases