title: The effect of oxidative stress on gene expression of Shiga toxin-producing Escherichia coli (STEC) O157:H7 and non-O157 serotypes.
abstract: Understanding the survival mechanisms used by Shiga toxin-producing Escherichia coli (STEC), including O157:H7 and non-O157 serotypes, is important for minimizing contamination of fresh produce and occurrence of foodborne outbreaks. Recent outbreaks linked to leafy green vegetables and sprouted seeds have prompted researchers to focus on investigating decontamination strategies. Several studies showed that hydrogen peroxide (H2O2) treatment has been effective in reducing pathogens on fresh produce. As such, the effect of hydrogen peroxide on stress-associated and virulence gene expression in six STEC isolates was investigated in this study. Logarithmic phase cells of E. coli O157:H7 (EDL933) and non-O157 serotypes, including E. coli O26:H11 (EC20070549), O103:H2 (EC19970811), O104:H4 (NML#11-3088), O111:NM (EC20070546) and O145:NM (EC19970355) were exposed to 2.5mM H2O2 for 40 min and gene expression was evaluated using quantitative real-time PCR. Different patterns of gene expression were observed in E. coli O157:H7 and non-O157 serotypes. Particularly, Shiga toxin gene stx2 was upregulated in O157:H7, but not in O104:H4. Moreover, stx1 was significantly upregulated in STEC O157:H7, but only slightly upregulated Stx1-positive non-O157 serotypes. However genes related to motility (fliC) and intimin gene (eae) were downregulated in most strains. Stress-associated sodA gene encoding manganese superoxide dismutase was significantly upregulated in all serotypes. The dps gene coding for non-specific DNA binding protein was upregulated in O145:NM, O111:NM, O103:H2 and O26:H11. However genes related to cold shock (cspC) and acid resistance (gadW) were significantly downregulated in all strains tested. The results of this study provide a basic understanding of the oxidative stress impact on survival and virulence of non-O157 serotype STEC strains.
authors: Agriculture and Agri-Food Canada, Guelph Food Research Center, 93 Stone Road West, Guelph, Ontario, N1G 5C9, Canada.
authors: Gui-Ying
authors: GY
authors: Mei
authors: Agriculture and Agri-Food Canada, Guelph Food Research Center, 93 Stone Road West, Guelph, Ontario, N1G 5C9, Canada.
authors: Joshua
authors: J
authors: Tang
authors: Agriculture and Agri-Food Canada, Guelph Food Research Center, 93 Stone Road West, Guelph, Ontario, N1G 5C9, Canada.
authors: Christine
authors: C
authors: Carey
authors: Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, PO Box 5000, 4200 Highway 97, Summerland, British Columbia, V0H 1Z0, Canada.
authors: Susan
authors: S
authors: Bach
authors: Agriculture and Agri-Food Canada, Guelph Food Research Center, 93 Stone Road West, Guelph, Ontario, N1G 5C9, Canada. Electronic address: magdalena.kostrzynska@agr.gc.ca.
authors: Magdalena
authors: M
authors: Kostrzynska
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress / Q000235:genetics*; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000890:Anti-Infective Agents; D029968:Escherichia coli Proteins; D037521:Virulence Factors; D006861:Hydrogen Peroxide
keywords: Gene expression; Hydrogen peroxide (PubChem CID: 784); Non-O157 serotypes; Oxidative stress; Shiga toxin-producing Escherichia coli (STEC)