Bile-salt-mediated Induction of Antimicrobial and Bile Resistance in Salmonella Typhimurium

Microbiology. 2004 Apr;150(Pt 4):775-783. doi: 10.1099/mic.0.26769-0.


By DNA microarray, the Salmonella typhimurium marRAB operon was identified as being bile-activated. Transcriptional assays confirm that marRAB is activated in the presence of bile and that this response is concentration-dependent. The bile salt deoxycholate is alone able to activate transcription, while there was no response in the presence of other bile salts tested or a non-ionic detergent. Deoxycholate is able to interact with MarR and interfere with its ability to bind to the mar operator. In addition, incubation of salmonellae in the presence of sublethal concentrations of bile is able to enhance resistance to chloramphenicol and bile, by means of both mar-dependent and mar-independent pathways. To further characterize putative marRAB-regulated genes that may be important for the resistance phenotype, acrAB, which encodes an efflux pump, was analysed. In S. typhimurium, acrAB is required for bile resistance, but while transcription of acrAB is activated by bile, this activation is independent of marRAB, as well as Rob, RpoS or PhoP-PhoQ. These data suggest that bile interacts with salmonellae to increase resistance to bile and other antimicrobials and that this can occur by marRAB- and acrAB-dependent pathways that function independently with respect to bile activation.

Publication types

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

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bile Acids and Salts / pharmacology*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Deoxycholic Acid / pharmacology
  • Drug Resistance, Multiple, Bacterial*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Gene Expression Regulation, Bacterial*
  • Microbial Sensitivity Tests
  • Oligonucleotide Array Sequence Analysis
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Salmonella typhimurium / drug effects*
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Bile Acids and Salts
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • MarA protein, E coli
  • MarR protein, E coli
  • Repressor Proteins
  • Deoxycholic Acid