Effect of exposure to hydrogen peroxide on the virulence of Escherichia coli

Purpose: To eliminate pathogenic bacteria, the host presents conditions that are stressful for bacteria. Oxidative stress arises when the concentration of pro-oxidants like hydrogen peroxide (H₂O₂ ) and superoxide anion increases to a level over the basal defence capacity of the cell. In the present study, we studied the effect of oxidative stress on the production of certain virulence factors by Escherichia coli. Methods: E. coli was exposed to oxidative stress by growing in the presence of different concentrations of H₂O₂. The effect of oxidative stress on the expression of surface hydrophobicity, adherence, haemolysin production, serum resistance and phagocytosis was studied. Results: Oxidative stress caused a significant decrease in the expression of all the virulence factors of E. coli. Conclusions: Synthesis of virulence factors can be significantly altered by oxidative stress and such changes may affect the pathogenicity of E. coli.