title: Organic solvent-tolerant mutants of Pseudomonas aeruginosa display multiple antibiotic resistance.
abstract: Organic solvent-tolerant mutants of Pseudomonas aeruginosa selected in the presence of hexane exhibited increased resistance to a variety of structurally unrelated antimicrobial agents, including beta-lactams, fluoroquinolones, chloramphenicol, tetracycline, and novobiocin, a phenotype typical of nalB multidrug-resistant mutants. Western immunoblotting with antibodies specific to components of the three known multidrug efflux systems in P. aeruginosa demonstrated that the solvent-tolerant mutants displayed increased expression of the MexAB-OprM system and decreased expression of the MexEF-OprN system. Sequence analysis of mexR, the repressor gene of mexAB-oprM efflux operon, identified a nonsense mutation and a point mutation in the mexR genes of two solvent-tolerant mutants. These results emphasize the importance of the MexAB-OprM efflux system in organic solvent tolerance and the ability of environmental pollutants to select bacteria with a medically relevant antibiotic-resistant phenotype.
authors.affiliation: Department of Microbiology and Immunology, Queen's University, Kingston, ON, Canada.
authors.forename: X Z
authors.initials: XZ
authors.lastname: Li
authors.forename: K
authors.initials: K
authors.lastname: Poole
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015153:Blotting, Western; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006586:Hexanes / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D012997:Solvents / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D006586:Hexanes; D012097:Repressor Proteins; D012997:Solvents