The impact of oregano (Origanum heracleoticum) essential oil and carvacrol on virulence gene transcription by Escherichia coli O157:H7

FEMS Microbiol Lett. 2015 Jan;362(1):1-7. doi: 10.1093/femsle/fnu021. Epub 2014 Dec 4.


The aim of the current study was to determine, via reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis, the effect of oregano essential oil (Origanum heracleoticum) and carvacrol, its major component, on the expression of virulence-associated genes in enterohaemorrhagic Escherichia coli (EHEC) O157:H7 ATCC strain 35150. Both oregano oil and carvacrol demonstrated their efficacy firstly, by inhibiting the transcription of the ler gene involved in upregulation of the LEE2, LEE3 and LEE4 promoters and of attaching and effacing lesions and secondly by decreasing both Shiga toxin and fliC genes expression. In addition, a decrease in luxS gene transcription involved in quorum sensing was observed. These results were dose dependent and showed a specific effect of O. heracleoticum and carvacrol in downregulating the expression of virulence genes in EHEC O157:H7. These findings suggest that oregano oil and carvacrol have the potential to mitigate the adverse health effects caused by virulence gene expression in EHEC O157:H7, through the use of these substances as natural antibacterial additives in foods or as an alternative to antibiotics.

Keywords: EHEC O157:H7; Oregano essential oil; carvacrol; virulence gene expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / isolation & purification
  • Anti-Bacterial Agents / metabolism*
  • Cymenes
  • Escherichia coli O157 / drug effects*
  • Escherichia coli Proteins / biosynthesis
  • Gene Expression / drug effects*
  • Monoterpenes / isolation & purification
  • Monoterpenes / metabolism*
  • Oils, Volatile / isolation & purification
  • Oils, Volatile / metabolism*
  • Origanum / chemistry*
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription, Genetic / drug effects
  • Virulence Factors / biosynthesis*


  • Anti-Bacterial Agents
  • Cymenes
  • Escherichia coli Proteins
  • Monoterpenes
  • Oils, Volatile
  • Virulence Factors
  • carvacrol