title: Physiological characterisation of the efflux pump system of antibiotic-susceptible and multidrug-resistant Enterobacter aerogenes.
abstract: Enterobacter aerogenes predominates amongst Enterobacteriaceae species that are increasingly reported as producers of extended-spectrum beta-lactamases. Although this mechanism of resistance to beta-lactams is important, other mechanisms bestowing a multidrug-resistant (MDR) phenotype in this species are now well documented. Amongst these mechanisms is the overexpression of efflux pumps that extrude structurally unrelated antibiotics prior to their reaching their targets. Interestingly, although knowledge of the genetic background behind efflux pumps is rapidly advancing, few studies assess the physiological nature of the overall efflux pump system of this, or for that matter any other, bacterium. The study reported here evaluates physiologically the efflux pump system of an E. aerogenes ATCC reference as well as two strains whose MDR phenotypes are mediated by overexpressed efflux pumps. The activities of the efflux pumps in these strains are modulated by pH and glucose, although the effects of the latter are essentially restricted to pH 8, suggesting the presence of two general efflux pump systems, i.e. proton-motive force-dependent and ABC transporter types, respectively.
authors.affiliation: Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Martins
authors.forename: G
authors.initials: G
authors.lastname: Spengler
authors.forename: M
authors.initials: M
authors.lastname: Martins
authors.forename: L
authors.initials: L
authors.lastname: Rodrigues
authors.forename: M
authors.initials: M
authors.lastname: Viveiros
authors.forename: A
authors.initials: A
authors.lastname: Davin-Regli
authors.forename: J
authors.initials: J
authors.lastname: Chevalier
authors.forename: I
authors.initials: I
authors.lastname: Couto
authors.forename: J M
authors.initials: JM
authors.lastname: Pagès
authors.forename: L
authors.initials: L
authors.lastname: Amaral
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism*; D024901:Drug Resistance, Multiple, Bacterial; D021902:Enterobacter aerogenes / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D004996:Ethidium / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D018892:Proton-Motive Force; D015854:Up-Regulation
chemical_list: D018528:ATP-Binding Cassette Transporters; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004996:Ethidium; D005947:Glucose