Evidence for an efflux pump mediating multiple antibiotic resistance in Salmonella enterica serovar Typhimurium

L J Piddock, D G White, K Gensberg, L Pumbwe, D J Griggs

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109 Citations (Scopus)


The mechanism of multiple antibiotic resistance in six isolates of Salmonella enterica serovar Typhimurium recovered from a patient treated with ciprofloxacin was studied to investigate the role of efflux in the resistance phenotype. Compared to the patient's pretherapy isolate (L3), five of six isolates accumulated less ciprofloxacin, three of six isolates accumulated less chloramphenicol, and all six accumulated less tetracycline. The accumulation of one or more antibiotics was increased by carbonyl cyanide m-chlorophenylhydrazone to concentrations similar to those accumulated by L3 for all isolates except one, in which accumulation of all three agents remained approximately half that of L3. All isolates had the published wild-type sequences of marO and marR. No increased expression of marA, tolC, or soxS was observed by Northern blotting; however, three isolates showed increased expression of acrB, which was confirmed by quantitative competitive reverse transcription-PCR. However, there were no mutations within acrR or the promoter region of acrAB in any of the isolates.
Original languageEnglish
Pages (from-to)3118-21
Number of pages4
JournalAntimicrobial Agents and Chemotherapy
Issue number11
Publication statusPublished - Nov 2000


  • Bacterial Proteins
  • Biological Transport
  • Carrier Proteins
  • DNA-Binding Proteins
  • Drug Resistance, Microbial
  • Drug Resistance, Multiple
  • Escherichia coli Proteins
  • Humans
  • Membrane Proteins
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Multidrug Resistance-Associated Proteins
  • Repressor Proteins
  • Salmonella enterica


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