Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2013
Publication Date: 6/20/2013
Citation: Moreau, M.R., Cote, R., Katani, R., Kudva, I.T., Carter, M.Q., Brandl, M., Kapur, V. 2013. Genomic and molecular analysis of the hyperadherent phenotype of an Escherichia coli O157:H7 super shedder isolate [abstract]. In: Proceedings of Molecular Biology, Sensing and Signaling Across the Mucosa: From Homeostasis to Pathogenesis, June 4-6, 2013, University Park, Pennsylvania. p. 92. Interpretive Summary:
Technical Abstract: Shiga Toxin producing Escherichia coli (STEC) are a subtype of pathogenic E. coli and, in particular, STEC isolates of E. coli serotype O157:H7 are recognized as a major foodborne pathogen that can cause infections ranging from having simple intestinal discomfort to bloody diarrhea and life threatening Hemolytic Uremic Syndrome. The primary reservoir for O157:H7 are asymptomatic cattle. E. coli O157:H7 major site of colonization in cattle is 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 shed from the cattle. Super shedding (SS) is a phenomenon that has been reported in some cattle that shed this organism at a rate greater than 10^4 colony forming units per gram (CFU/G), orders-of-magnitude greater than the normal shedding levels of 10-100 CFU/g. Recently, a representative SS isolate, SS17, was fully sequenced and analyzed for SNPs across the genome and particularly in virulence and adherence related genes. This analysis revealed that SS17 contained 295 virulence related genes, of which 39 had coding non-synonymous SNPs (nsSNPs). O157:H7 employs a series of genes belonging to the locus of enterocyte effacement (LEE), which is critical for the intimate attachment of the bacteria to human host intestinal epithelia. The development of a unique cattle RAJ cell culture model revealed that O157:H7 employ a LEE-independent mechanism of attachment to the recto-anal squamous epithelial (RSE) cells. SS isolates have a strong aggregative and adherence phenotype on RAJ cells, as opposed to two other O157:H7 strains 86-24 and EDL933. Other data show that these SS isolates have a higher affinity of binding leafy greens, such as lettuce and spinach, which is important as contaminated leafy greens serve as another major source of transmission of this pathogen. The SNP analysis coupled with a proteome in DMEM and microarray data from binding on plants, produced a triaged list of targeted knockouts to start to identify changes which could explain the change in the adherence and aggregation phenotype on the RAJ and plant models. Our hypothesis is that there are nsSNPs in virulence related microbial factors in the super shedder compared to a reference genome.