title: SmvA, and not AcrB, is the major efflux pump for acriflavine and related compounds in Salmonella enterica serovar Typhimurium.
abstract: OBJECTIVE
  The aim was to study the role played by SmvA pump in the efflux of quaternary ammonium compounds (QACs) in Salmonella enterica serovar Typhimurium (Salmonella Typhimurium).
  
  
  METHODS
  Mutants in the smvA, acrB and tolC genes were constructed by the red swap method. P22 was used to transduce tolC to acrB and smvA mutant strains. The susceptibility of these strains to acriflavine and a variety of QACs was determined by MIC assays.
  
  
  RESULTS
  In comparison with the Salmonella Typhimurium wild-type strain, the smvA mutant was more susceptible to QACs than the acrB mutant strain. A tolC single mutant was more susceptible than an acrB mutant to QACs, acriflavine, ethidium bromide, malachite green and pyronin B. The tolC-acrB double mutant was as susceptible as the single tolC mutant to QACs. Additionally, the smvA mutant strain was more susceptible to acriflavine than the acrB mutant (MICs = 31.3 versus 125 mg/L, i.e. 4-fold). Finally, the tolC-smvA double mutant (3.9 mg/L) was approximately 10 times more susceptible to acriflavine than either smvA (31.3 mg/L) or tolC (31.3 mg/L) single mutants.
  
  
  CONCLUSIONS
  It is the SmvA efflux pump, and not AcrB, that plays the major role in the efflux of acriflavine and other QACs from Salmonella Typhimurium. This apparently conflicting report is due to the fact that in Escherichia coli the smvA gene does not exist. Our results suggest that tolC and smvA genes encode components of two different efflux systems with overlapping specificities that work in parallel to export acriflavine and other QACs.
authors.affiliation: Laboratorio de Microbiología, Departamento de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors.forename: Nicolás A
authors.initials: NA
authors.lastname: Villagra
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Hidalgo
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Santiviago
authors.forename: Claudia P
authors.initials: CP
authors.lastname: Saavedra
authors.forename: Guido C
authors.initials: GC
authors.lastname: Mora
mesh_terms: D000167:Acriflavine / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004996:Ethidium / Q000378:metabolism / Q000494:pharmacology; D017353:Gene Deletion; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D016254:Mutagenesis, Insertional; D018272:Porins / Q000235:genetics* / Q000378:metabolism*; D011754:Pyronine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology; D012394:Rosaniline Dyes / Q000378:metabolism / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism*
chemical_list: C474926:AcrB protein, Salmonella enterica; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D018272:Porins; D000644:Quaternary Ammonium Compounds; D012394:Rosaniline Dyes; C470932:SmvA protein, Salmonella typhimurium; C005095:malachite green; D000167:Acriflavine; D004996:Ethidium; C012020:pyronine B; D011754:Pyronine