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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #428281
Research Project: Intestinal Microbial Ecology and Non-Antibiotic Strategies to Limit Shiga Toxin-Producing Escherichia coli (STEC) and Antimicrobial Resistance Transmission in Food Animals

Location: Food Safety and Enteric Pathogens Research

Title: Profiles & peroxide: Transcriptional program of super shedder E. coli O157:H7 results in increased resistance to hydrogen peroxide

Author
item MADISON, REILLY - Providence College
item DOWLING, ELIZA - Providence College
item DALESSANDRO, OLIVIA - Providence College
item BIERNBAUM, ERIKA - Oak Ridge Institute For Science And Education (ORISE)
item Kudva, Indira
item MOREAU, MATHEW - Providence College

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Enterohermorrhagic Escherichia coli. (EHEC) serovar O157:H7 (Ec-O157:H7) is a shiga-toxin producing E. coli (STEC), the secretion of which is responsible for symptoms of its infection including bloody diarrhea and hemolytic uremic syndrome (HUS). Cattle serve as the primary and asymptomatic reservoir for O157:H7, which colonize their recto-anal junction (RAJ). While cattle typically shed EHEC at a rate of approx. 100 CFU/g of feces, super-shedders (SS) excrete more than 1.0 x 104 CFU/g. This SS phenotype greatly increases environmental burden and raises the risk of transmission. Two strains of Ec-O157:H7, an SS (SS17) and a non-SS (EDL933) attached to bovine RAJ squamous epithelial (RSE) cells were subjected to RNA sequencing (RNAseq) and comparative transcriptomics. The comparison of RSE cell-adherent SS17 and EDL933 transcriptomes revealed SS17 upregulates several genes involved in iron acquisition/metabolism, stress responses, and transport in comparison to EDL933. Genes that are downregulated in SS17 include those involved in metabolism, host interactions/virulence, and translation. Of particular interest was the observed upregulation of katG, a bifunctional catalase and peroxidase alongside the upregulation of iron acquisition genes and whether or not this change would result in an increased resistance to hydrogen peroxide. To test if this increased expression of katG and/or iron acquisition genes altered the isolates’ response to oxidative stress, SS17 and EDL933 were grown in the presence of various concentrations of hydrogen peroxide. At 35mM hydrogen peroxide, SS17 showed resilience to cell killing by increasing in turbidity and cell viability, whereas EDL933 does not. Despite this breakpoint, both strains showed remarkable resistance to killing by H2O2 compared to the K12 lab strain, which exhibits cell death at 1mM. These results show yet another unique trait associated with the SS phenotype that also increases their survivability and potential for transmission, infection, and disease by being able to overcome a fundamental aspect of eukaryotic immunity.