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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 #431774
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: Varied influence of curli and non-curli factors on Shiga toxin-producing Escherichia coli biofilm formation and animal cell adherence

Author
item Kudva, Indira
item BIERNBAUM, ERIKA - Oak Ridge Institute For Science And Education (ORISE)
item BARI, S.M. NAYEEMUL - Oak Ridge Institute For Science And Education (ORISE)
item DRABEK, KOY - Oak Ridge Institute For Science And Education (ORISE)
item MAZON, HANNAH - Former ARS Employee
item Bayles, Darrell

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/4/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Asymptomatic cattle and environmental biofilms act as reservoirs for the foodborne pathogen Shiga toxin-producing Escherichia coli (STEC) in animal production environments. While curli fimbriae are known to drive biofilm formation, their role in STEC adherence to the bovine recto-anal junction squamous epithelial (RSE) cells remains unclear. This study evaluated STEC O157, O26, and O111 isolates with diverse DNA fingerprints and phenotypes to investigate the relationship between curli, biofilms, and RSE cell adherence. The STEC isolates classified as curli-positive (C+), curli-negative (C-) or curli-variant (C+/C-). All C+ isolates produced biofilms at 26°C in LB-no salt (LB-NS) media. Although the genes involved in curli biogenesis (csgA-F) were present in all isolates, csgA exhibited serotype-specific mutations and down-regulation in C- isolates as determined by microscopy and RT-qPCR. Adherence assays using RSE cells demonstrated an aggregative-strong adherence phenotype for the O157 and O111 isolates, while the O26 isolates showed diffuse-moderate/ diffuse-strong adherence. Crucially, these patterns persisted regardless of curli or LB-NS-biofilm phenotypes, suggesting that factors other than curli mediate RSE cell attachment. To identify these factors, we analyzed biofilm formation in DMEM-low glucose (D-LG) media used for adherence assays, sequences of curli regulatory (rpoS, rcsB, mlrA) and cellulose expression (bcsA-B) genes, and transcriptomes of select STEC isolates grown under adherence assay conditions. In D-LG media, biofilms were weak across both C+ and C- isolates at 37°C. Sequence analysis of curli regulatory genes mostly revealed silent mutations, though some C- isolates possessed rpoS mutations leading to premature stop codons. While mlrA sequences differed between O157 and non-O157 serotypes, this did not impact curli expression. The presence of functional bcsA-B genes likely contributed to the weak biofilms observed in C- isolates. Transcriptome analysis is underway to identify additional adherence-related factors. These results indicate that STEC biofilm formation and RSE cell adherence are influenced by a complex interplay of curli and non-curli factors. These influences do not always correlate with genotypes, which can confound standard assays and highlights the need for a deeper understanding of STEC persistence.