title: Evidence of an efflux pump in Serratia marcescens.
abstract: Spontaneous mutants resistant to fluoroquinolones were obtained by exposing Serratia marcescens NIMA (wild-type strain) to increasing concentrations of ciprofloxacin both in liquid and on solid media. Frequencies of mutation ranged from 10(-7) to 10(-9). Active expulsion of antibiotic was explored as a possible mechanism of resistance in mutants as well as changes in topoisomerase target genes. The role of extrusion mechanisms in determining the emergence of multidrug-resistant bacteria was also examined. Mutants resistant to high concentrations of fluoroquinolones had a single mutation in their gyrA QRDR sequences, whereas the moderate resistance in the rest of mutants was due to extrusion of the drug.
authors.affiliation: Microbiology Unit, University of Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Berlanga
authors.forename: J L
authors.initials: JL
authors.lastname: Vázquez
authors.forename: J
authors.initials: J
authors.lastname: Hernandez-Borrell
authors.forename: M T
authors.initials: MT
authors.lastname: Montero
authors.forename: M
authors.initials: M
authors.lastname: Viñas
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000378:metabolism / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001483:Base Sequence; D002463:Cell Membrane Permeability; D002939:Ciprofloxacin / Q000378:metabolism / Q000494:pharmacology*; D003470:Culture Media; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D012706:Serratia marcescens / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D001425:Bacterial Outer Membrane Proteins; D003470:Culture Media; D008070:Lipopolysaccharides; D002939:Ciprofloxacin; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II