Expression of multidrug efflux pump genes acrAB-tolC, mdfA, and norE in Escherichia coli clinical isolates as a function of fluoroquinolone and multidrug resistance

Antimicrob Agents Chemother. 2011 Feb;55(2):921-4. doi: 10.1128/AAC.00996-10. Epub 2010 Nov 22.


In a single quantitative study, we measured acrA, acrB, tolC, mdfA, and norE expression in Escherichia coli clinical isolates by using real-time PCR. acrA and acrB overexpression strongly correlated with fluoroquinolone and multidrug resistance; tolC, mdfA, and norE expression did not. The order of abundance of efflux pump transcripts in all fluoroquinolone-susceptible isolates was tolC (highest), then acrA and acrB, and then mdfA and norE. Our findings suggest acrAB overexpression is an indicator of multidrug resistance.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Escherichia coli / drug effects*
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Fluoroquinolones / pharmacology*
  • Gene Expression Regulation, Bacterial*
  • Humans
  • Lipoproteins / genetics
  • Lipoproteins / metabolism
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Microbial Sensitivity Tests
  • Multidrug Resistance-Associated Proteins / genetics
  • Multidrug Resistance-Associated Proteins / metabolism


  • AcrA protein, E coli
  • AcrB protein, E coli
  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • Fluoroquinolones
  • Lipoproteins
  • Mdfa protein, E coli
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins
  • tolC protein, E coli