Variation of the mexT gene, a regulator of the MexEF-oprN efflux pump expression in wild-type strains of Pseudomonas aeruginosa

FEMS Microbiol Lett. 2000 Nov 1;192(1):107-12. doi: 10.1111/j.1574-6968.2000.tb09367.x.


We found three variations of wild-type strains in terms of mexT-mediated regulation of the MexEF-OprN efflux pump, in which overexpression of the pump results in nfxC-type antibiotic resistance in Pseudomonas aeruginosa. Type-I: the mexT gene of the wild-type strain encoded inactive MexT and the nfxC-type mutants derived from this parent had an additional mutation in mexT converting MexT from the inactive to the active form. Type-II: The mexT gene in the wild-type strain had an 8-bp insert producing inactive MexT and the nfxC-type mutants from this parent had a deletion of the 8-bp insert converting inactive MexT to the active form. Type-III: Both the wild-type strain and its nfxC-type derivative produced identical and active MexT. The nfxC mutant from this parent must have an additional mutation. The original nfxC mutant isolated in 1990 might be derived from the Type-I parent strain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Chloramphenicol / pharmacology
  • Drug Resistance, Microbial / genetics
  • Drug Resistance, Multiple / genetics
  • Gene Expression Regulation, Bacterial / genetics
  • Genes, Bacterial
  • Genes, Regulator / genetics
  • Imipenem / pharmacology
  • Microbial Sensitivity Tests / methods
  • Molecular Sequence Data
  • Mutation
  • Pseudomonas aeruginosa / drug effects*
  • Pseudomonas aeruginosa / genetics*
  • Sequence Analysis, DNA / methods
  • Trans-Activators / genetics*
  • Trans-Activators / metabolism


  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • OprN protein, Pseudomonas aeruginosa
  • Trans-Activators
  • Chloramphenicol
  • Imipenem

Associated data

  • GENBANK/AJ007825