title: Comparative analysis of super-shedder strains of Escherichia coli O157:H7 reveals distinctive genomic features and a strongly aggregative adherent phenotype on bovine rectoanal junction squamous epithelial cells.
abstract: Shiga toxin-producing Escherichia coli O157:H7 (O157) are significant foodborne pathogens and pose a serious threat to public health worldwide. The major reservoirs of O157 are asymptomatic cattle which harbor the organism in the terminal recto-anal junction (RAJ). Some colonized animals, referred to as "super-shedders" (SS), are known to shed O157 in exceptionally large numbers (>104 CFU/g of feces). Recent studies suggest that SS cattle play a major role in the prevalence and transmission of O157, but little is known about the molecular mechanisms associated with super-shedding. Whole genome sequence analysis of an SS O157 strain (SS17) revealed a genome of 5,523,849 bp chromosome with 5,430 open reading frames and two plasmids, pO157 and pSS17, of 94,645 bp and 37,446 bp, respectively. Comparative analyses showed that SS17 is clustered with spinach-associated O157 outbreak strains, and belongs to the lineage I/II, clade 8, D group, and genotype 1, a subgroup of O157 with predicted hyper-virulence. A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence- and virulence-related loci. Phenotypic analyses revealed a distinctive and strongly adherent aggregative phenotype of SS17 on bovine RAJ stratified squamous epithelial (RSE) cells that was conserved amongst other SS isolates. Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism. Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Rebecca
authors: R
authors: Cote
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Robab
authors: R
authors: Katani
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Matthew R
authors: MR
authors: Moreau
authors: Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa, United States of America.
authors: Indira T
authors: IT
authors: Kudva
authors: Roman L. Hruska U.S. Meat Animal Research Center, Agricultural Research Service, U.S. Department of Agriculture, Clay Center, Nebraska, United States of America.
authors: Terrance M
authors: TM
authors: Arthur
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; E. coli Reference Center, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Chitrita
authors: C
authors: DebRoy
authors: The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America; Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Michael M
authors: MM
authors: Mwangi
authors: The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America; Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Istvan
authors: I
authors: Albert
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Juan Antonio
authors: JA
authors: Raygoza Garay
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Lingling
authors: L
authors: Li
authors: Produce Safety and Microbiology, Research Unit, Agriculture Research Service, U.S. Department of Agriculture, Albany, California, United States of America.
authors: Maria T
authors: MT
authors: Brandl
authors: Produce Safety and Microbiology, Research Unit, Agriculture Research Service, U.S. Department of Agriculture, Albany, California, United States of America.
authors: Michelle Q
authors: MQ
authors: Carter
authors: Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors: Vivek
authors: V
authors: Kapur
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D057138:Bacterial Shedding / Q000235:genetics*; D001483:Base Sequence; D002417:Cattle / Q000382:microbiology*; D004847:Epithelial Cells / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D016680:Genome, Bacterial; D005838:Genotype; D007420:Intestine, Large / Q000382:microbiology*; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids; D011110:Polymorphism, Genetic; D012007:Rectum / Q000382:microbiology; D014774:Virulence / Q000235:genetics