Contributions of MexAB-OprM and an EmrE homolog to intrinsic resistance of Pseudomonas aeruginosa to aminoglycosides and dyes

Antimicrob Agents Chemother. 2003 Jan;47(1):27-33. doi: 10.1128/AAC.47.1.27-33.2003.

Abstract

Of the six putative small multidrug resistance (SMR) family proteins of Pseudomonas aeruginosa, a protein encoded by the PA4990 gene (emrE(Pae)) shows the highest identity to the well-characterized EmrE efflux transporter of Escherichia coli. Reverse transcription-PCR confirmed the expression of emrE(Pae) in the wild-type strain of P. aeruginosa. Using isogenic emrE(Pae), mexAB-oprM, and/or mexB deletion mutants, the contributions of the EmrE protein and the MexAB-OprM efflux system to drug resistance in P. aeruginosa were assessed by a drug susceptibility test carried out in a low-ionic-strength medium, Difco nutrient broth. We found that EmrE(Pae) contributed to intrinsic resistance not only to ethidium bromide and acriflavine but also to aminoglycosides. In this low-ionic-strength medium, MexAB-OprM was also shown to contribute to aminoglycoside resistance, presumably via active efflux. Aminoglycoside resistance caused by these two pumps could not be demonstrated in high-ionic-strength media, such as Luria broth or Mueller-Hinton broth. The EmrE-dependent efflux of ethidium bromide was confirmed by a continuous fluorescence assay.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Aminoglycosides
  • Anti-Bacterial Agents / pharmacology*
  • Antiporters / drug effects
  • Antiporters / genetics*
  • Bacterial Outer Membrane Proteins / drug effects
  • Bacterial Outer Membrane Proteins / genetics*
  • Carrier Proteins / drug effects
  • Carrier Proteins / genetics*
  • Drug Resistance, Bacterial / genetics*
  • Escherichia coli Proteins
  • Membrane Proteins / drug effects
  • Membrane Proteins / genetics*
  • Membrane Transport Proteins*
  • Microbial Sensitivity Tests
  • Plasmids
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / genetics*

Substances

  • Aminoglycosides
  • Anti-Bacterial Agents
  • Antiporters
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • MexA protein, Pseudomonas aeruginosa
  • EmrE protein, E coli