title: Penicillin-binding proteins, porins and outer-membrane permeability of carbenicillin-resistant and -susceptible strains of Pseudomonas aeruginosa.
abstract: Reduced cell permeability and target penicillin-binding protein modification were investigated as mechanisms of intrinsic resistance in strains of Pseudomonas aeruginosa resistant to carbenicillin (MIC greater than 128 mg/L) independently of beta-lactamase production. The carbenicillin-resistant strains were also remarkably resistant to other beta-lactams, quinolones, tetracyline and chloramphenicol, whereas carbenicillin-hypersusceptible strains (MIC less than 2 mg/L) were very sensitive to these antimicrobial compounds. These observations suggested a non-specific mechanism of resistance involving reduced permeability of the outer layers of the bacterial cell. However, carbenicillin-resistant and carbenicillin-sensitive strains had identical porin levels and the target penicillin-binding proteins of carbenicillin-resistant (MIC 256-2048 mg/L), carbenicillin-sensitive (MIC 64 mg/L) and carbenicillin-hypersusceptible (MIC 0.015 mg/L) strains were equally sensitive to beta-lactams. Thus, subtle changes in porin function or additional outer-membrane barriers regulating permeability may be involved in intrinsic resistance.
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis*; D001426:Bacterial Proteins / Q000032:analysis*; D002228:Carbenicillin / Q000494:pharmacology*; D002268:Carboxypeptidases / Q000032:analysis*; D002352:Carrier Proteins / Q000032:analysis*; D002463:Cell Membrane Permeability; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis*; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D018272:Porins; D011550:Pseudomonas aeruginosa / Q000032:analysis / Q000187:drug effects* / Q000502:physiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D018272:Porins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002268:Carboxypeptidases; D002267:Muramoylpentapeptide Carboxypeptidase; D002228:Carbenicillin