title: Penetration of the outer membrane of Pseudomonas aeruginosa by synergistic combinations of beta-lactam and aminoglycoside antibiotics.
abstract: The mechanism of the synergistic action of carbenicillin-gentamicin and moxalactam-tobramycin combinations against Pseudomonas aeruginosa ATCC 9027 was investigated. Disruption of the outer membrane penetration barrier by EDTA treatment enhanced the activity of both combinations against the cells during growth for 100 min in exponential phase. However, there was no loss of the synergistic activity of the antibiotics as a result of this treatment. A procedure involving minimal inhibitory concentration testing in the presence of rifampin did not detect any destabilization of the outer membrane barrier by any of the four drugs over an 18-h period. The combined evidence indicates that beta-lactamaminoglycoside synergy is not mediated by the outer membrane of this organism.
mesh_terms: D000617:Aminoglycosides / Q000378:metabolism / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004338:Drug Combinations; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000378:metabolism*; D047090:beta-Lactams / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D047090:beta-Lactams; D004492:Edetic Acid