Acid-stress-induced Changes in Enterohaemorrhagic Escherichia Coli O157 : H7 Virulence

Microbiology. 2009 Sep;155(Pt 9):2907-2918. doi: 10.1099/mic.0.025171-0. Epub 2009 Jun 4.


Enterohaemorrhagic Escherichia coli (EHEC) O157 : H7 is naturally exposed to a wide variety of stresses including gastric acid shock, and yet little is known about how this stress influences virulence. This study investigated the impact of acid stress on several critical virulence properties including survival, host adhesion, Shiga toxin production, motility and induction of host-cell apoptosis. Several acid-stress protocols with relevance for gastric passage as well as external environmental exposure were included. Acute acid stress at pH 3 preceded by acid adaptation at pH 5 significantly enhanced the adhesion of surviving organisms to epithelial cells and bacterial induction of host-cell apoptosis. Motility was also significantly increased after acute acid stress. Interestingly, neither secreted nor periplasmic levels of Shiga toxin were affected by acid shock. Pretreatment of bacteria with erythromycin eliminated the acid-induced adhesion enhancement, suggesting that de novo protein synthesis was required for the enhanced adhesion of acid-shocked organisms. DNA microarray was used to analyse the transcriptome of an EHEC O157 : H7 strain exposed to three different acid-stress treatments. Expression profiles of acid-stressed EHEC revealed significant changes in virulence factors associated with adhesion, motility and type III secretion. These results document profound changes in the virulence properties of EHEC O157 : H7 after acid stress, provide a comprehensive genetic analysis to substantiate these changes and suggest strategies that this pathogen may use during gastric passage and colonization in the human gastrointestinal tract.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Bacterial Adhesion / drug effects
  • Cell Line
  • Epithelial Cells / microbiology
  • Epithelial Cells / physiology
  • Erythromycin / pharmacology
  • Escherichia coli Infections / metabolism
  • Escherichia coli Infections / microbiology*
  • Escherichia coli O157 / drug effects
  • Escherichia coli O157 / pathogenicity*
  • Escherichia coli O157 / physiology
  • Gene Expression Profiling
  • Host-Pathogen Interactions / drug effects
  • Humans
  • Hydrogen-Ion Concentration
  • Protein Synthesis Inhibitors / pharmacology
  • Shiga Toxins / biosynthesis
  • Stress, Physiological*
  • Virulence
  • Virulence Factors / biosynthesis
  • Virulence Factors / genetics


  • Protein Synthesis Inhibitors
  • Shiga Toxins
  • Virulence Factors
  • Erythromycin

Associated data

  • GEO/GSE14069