Investigating the adherence factors of Escherichia coli at the bovine recto-anal junction

Authors: NAWROCKI, ERIN - Pennsylvania State University; Kudva, Indira; DUDLEY, EDWARD - Pennsylvania State University

Submitted to: Microbiology Spectrum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2024
Publication Date: 9/27/2024
Citation: Nawrocki, E.M., Kudva, I.T., Dudley, E.G. O. Investigating the adherence factors of Escherichia coli at the bovine recto-anal junction. Microbiol Spectr O:e01270-24. https://doi.org/10.1128/spectrum.01270-24.
DOI: https://doi.org/10.1128/spectrum.01270-24

Interpretive Summary: Shiga toxin-producing Escherichia coli (STEC) cause foodborne illness in humans but are present in cattle, the main source of infection, without causing disease. The mechanisms that STEC and other non-STEC E. coli, found in the cattle gut, use to adhere to cattle intestinal cells are largely unknown. Various strategies are being studied to control STEC in livestock and to limit the risk of outbreaks. These include vaccinating animals against STEC strains and supplementing their feed with probiotics to reduce the carriage of these bacteria. No strategy is completely effective, however, and probiotics often fail to colonize the animals. We isolated non-STEC E. coli from healthy cow intestines and showed that they could outcompete STEC when grown together. We sought to identify the genes required for E. coli adherence in cattle by quantifying attachment to bovine intestinal cells by a diverse set of bacteria. We propose that focused study of these non-STEC E. coli and their adherence factors will help design better probiotics for targeting STEC in livestock.

Technical Abstract: Shiga toxin–producing Escherichia coli (STEC) are major foodborne pathogens that cause thousands of hospitalizations each year in the United States. Cattle, the natural reservoir, harbor STEC asymptomatically at the recto-anal junction (RAJ). The molecular mechanisms that allow STEC and non-STEC E. coli to adhere to the RAJ are not fully understood, in part because most adherence studies utilize human cell culture models. To identify a set of bovine-specific E. coli adherence factors, we used the primary RAJ squamous epithelial (RSE) cell-adherence assay to co-culture RSE cells from healthy Holstein cattle with diverse E. coli strains from bovine and nonbovine sources. We hypothesized that a comparative genomic analysis of the strains would reveal factors associated with RSE adherence. After performing adherence assays with historical strains from the E. coli Reference Center and strains newly isolated from the RAJ, we used the bioinformatic tool Roary to create a pangenome of this collection. We classified strains as either low or high adherence and using the Scoary program compiled a list of accessory genes correlated with the “high adherence” strains. Several gene clusters were associated with the high adherence phenotype, including two that encode uncharacterized proteins. We also demonstrated that non-STEC E. coli strains from the RAJ are more adherent than other isolates and can reduce STEC adherence to RSEs in cocultures. Further analysis of the adherence-associated gene clusters may lead to an improved understanding of the molecular mechanisms of RSE adherence and may help develop probiotics targeting STEC in cattle.