Antibiotic resistance caused by gram-negative multidrug efflux pumps

Clin Infect Dis. 1998 Aug:27 Suppl 1:S32-41. doi: 10.1086/514920.


Minimum inhibitory concentrations (MICs) of most lipophilic agents tend to be much higher against gram-negative than gram-positive bacteria. Multidrug efflux pumps that traverse both the inner and outer membranes make a major contribution to this intrinsic resistance of gram-negative bacteria. Such a pump is composed of at least three components, is energized by the proton-motive force, and can pump out not only an extremely wide variety of detergents, dyes, and antibiotics, but also those compounds, such as beta-lactams, that do not easily cross the cytoplasmic membrane. Increased expression of these pumps can raise the MICs to an impressive level. For example, 80% of carbenicillin-resistant clinical isolates of Pseudomonas aeruginosa from the British Isles owed their resistance to overexpression of an efflux pump and had carbenicillin MICs that were up to 2,000 times higher than that of the pump-deficient mutant strain.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / metabolism*
  • Cell Membrane Permeability
  • Drug Resistance, Microbial*
  • Escherichia coli Proteins*
  • Evolution, Molecular
  • Gram-Negative Bacteria / drug effects
  • Gram-Negative Bacteria / metabolism*
  • Lipoproteins / metabolism
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins


  • AcrA protein, E coli
  • AcrB protein, E coli
  • Bacterial Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • Lipoproteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins