title: Evidence for the existence of a multidrug efflux transporter distinct from NorA in Staphylococcus aureus.
abstract: A Staphylococcus aureus norA disruption mutant was created by allelic replacement. Exposure of this mutant to norfloxacin produced SA K1748, a derivative with raised fluoroquinolone MICs, found to be the result of a grlA mutation, and raised organic cation MICs. Ethidium and enoxacin uptake was identical in SA K1748 and its parent, but pre-exposure of SA K1748 to organic cations caused a reduction in ethidium uptake as a result of increased efflux. Altered ethidium uptake and efflux, as well as increased MICs of other organic cations, suggest that SA K1748 possesses a non-NorA multidrug efflux transporter that is inducible by its substrates.
authors.affiliation: The John D. Dingell Department of Veteran's Affairs Medical Center, Division of Infectious Diseases, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. gkaatz@juno.com
authors.forename: G W
authors.initials: GW
authors.lastname: Kaatz
authors.forename: S M
authors.initials: SM
authors.lastname: Seo
authors.forename: L
authors.initials: L
authors.lastname: O'Brien
authors.forename: M
authors.initials: M
authors.lastname: Wahiduzzaman
authors.forename: T J
authors.initials: TJ
authors.lastname: Foster
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis*; D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D004996:Ethidium / Q000494:pharmacology; D024841:Fluoroquinolones; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D004996:Ethidium; D024841:Fluoroquinolones; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C075040:NorA protein, Staphylococcus