Non-fimbrial adhesin mutants reveal divergent Escherichia coli O157:H7 adherence mechanisms on human and cattle epithelial cells

Authors: MOREAU, MATHEW - Pennsylvania State University; Kudva, Indira; KATANI, ROBAB - Pennsylvania State University; COTE, REBECCA - Pennsylvania State University; LI, LINGLING - Pennsylvania State University; Arthur, Terrance; KAPUR, VIVEK - Pennsylvania State University

Submitted to: International Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2021
Publication Date: 1/29/2021
Citation: Moreau, M.R., Kudva, I.T., Katani, R., Cote, R., Li, L., Arthur, T.M., Kapur, V. 2021. Non-fimbrial adhesin mutants reveal divergent Escherichia coli O157:H7 adherence mechanisms on human and cattle epithelial cells. International Journal of Microbiology. 2021. Article 8868151. https://doi.org/10.1155/2021/8868151.
DOI: https://doi.org/10.1155/2021/8868151

Interpretive Summary: Shiga toxin-producing Escherichia coli O157:H7 (O157) asymptomatically colonize cattle and pose a major threat to human health through consumption of contaminated water and food. In cattle, O157 persists at the recto-anal junction (RAJ) found at the end of the bovine gastrointestinal tracts. Some of these cattle can be “super shedders” excreting O157 in high numbers in their feces. The unique cattle RAJ cell adherence model revealed that, unlike with human HEp-2 cells, O157 do not employ the well defined adherence protein, intimin, to attach to the RAJ squamous epithelial (RSE) cells. The adherence model also demonstrated that super shed O157 isolates adhere in unique strong aggregates to RSE cells. Ten adherence proteins were evaluated for their possible role in O157 attachment to both bovine RSE and human HEp-2 cells. Deleting the genes encoding these proteins had varying influence on the attachment of O157 to both cell types when created in a non-super shed isolate (EDL933) and a super shed isolate (SS17). Though none of these mutations were able to prevent adherence of super shed O157 to RSE cells, five gene deletions were able to confer the super shed adherence pattern to the non-super shedder isolate. In all, this study reveals that multiple proteins contribute to O157 adherence that vary according to the host (bovine or human) cell type and O157 isolate type.

Technical Abstract: Shiga toxin producing Escherichia coli (STEC) are a subtype of pathogenic E. coli, and STEC serotype O157:H7 (O157:H7) is a major foodborne pathogen causing symptoms ranging from simple intestinal discomfort to bloody diarrhea and life threatening hemolytic uremic syndrome. Asymptomatic cattle are colonized with O157:H7 at the mucosal interface of the recto-anal junction (RAJ), and coincidentally this colonization of the RAJ is critical for the ability of this organism to be shed from the cattle. Super shedding (SS) is a phenomenon that has been reported in some cattle that shed O157:H7 at a rate greater than 10 to the 4th colony forming units per gram of feces (CFU/g), 100-1000 times more or greater than normal shedders. The development of a unique cattle RAJ cell adherence model revealed that O157:H7 employ a LEE-independent mechanism of attachment to the other RAJ cell type, squamous epithelial (RSE) cells. Ten non-fimbrial adhesins were chosen through a selection process to determine their role in the unique super shedder adherence phenotypes to both bovine RSE and human HEp-2 cells. These mutations caused a multitude of phenotypic differences on both cell types when created in both a non-super shedder isolate (EDL933) and a super shedder isolate (SS17). Though none of these mutations were able to ablate adherence of SS17 to RSE cells, five gene deletions were able to confer super shedder phenotype to the non-super shedder isolate, EDL933. In all, this study reveals that adherence to cell type based on or independent of super shedder status is an intricate process with a complex intracellular regulatory network.