title: An RND-type multidrug efflux pump SdeXY from Serratia marcescens.
abstract: OBJECTIVE
  Serratia marcescens, an important cause of nosocomial infections, shows intrinsic resistance to a wide variety of antimicrobial agents (multidrug resistance). Multidrug efflux pumps are often involved in the multidrug resistance in many bacteria. A study was undertaken to characterize the multidrug efflux pumps in S. marcescens.
  
  
  METHODS
  The genes responsible for the multidrug resistance phenotype in S. marcescens were cloned into Escherichia coli KAM32, a drug-hypersusceptible strain, for further analysis.
  
  
  RESULTS
  We cloned sdeXY genes and determined the nucleotide sequence. Clones that carried the sdeXY genes displayed reduced susceptibility to several antimicrobial agents including erythromycin, tetracycline, norfloxacin, benzalkonium chloride, ethidium bromide, acriflavine and rhodamine 6G. A protein similarity search using GenBank revealed that SdeY is a member of the resistance nodulation cell-division (RND) family of multidrug efflux proteins and SdeX is a member of the membrane fusion proteins. Introduction of sdeXY into E. coli cells possessing tolC, but not in cells lacking tolC, resulted in multidrug resistance. We observed energy-dependent ethidium efflux in cells of E. coli KAM32 possessing sdeXY and tolC.
  
  
  CONCLUSIONS
  SdeXY is the first RND-type multidrug efflux pump to be characterized in multidrug-resistant S. marcescens.
authors.affiliation: Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Teruo
authors.initials: T
authors.lastname: Kuroda
authors.forename: Md Nazmul
authors.initials: MN
authors.lastname: Huda
authors.forename: Tohru
authors.initials: T
authors.lastname: Mizushima
authors.forename: Tomofusa
authors.initials: T
authors.lastname: Tsuchiya
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D012706:Serratia marcescens / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins