title: Coculture of Escherichia coli O157:H7 with a Nonpathogenic E. coli Strain Increases Toxin Production and Virulence in a Germfree Mouse Model.
abstract: Escherichia coli O157:H7 is a notorious foodborne pathogen due to its low infectious dose and the disease symptoms it causes, which include bloody diarrhea and severe abdominal cramps. In some cases, the disease progresses to hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS), due to the expression of one or more Shiga toxins (Stx). Isoforms of Stx, including Stx2a, are encoded within temperate prophages. In the presence of certain antibiotics, phage induction occurs, which also increases the expression of toxin genes. Additionally, increased Stx2 accumulation has been reported when O157:H7 was cocultured with phage-susceptible nonpathogenic E. coli. This study characterized an E. coli O157:H7 strain, designated PA2, that belongs to the hypervirulent clade 8 cluster. Stx2a levels after ciprofloxacin induction were lower for PA2 than for the prototypical outbreak strains Sakai and EDL933. However, during coculture with the nonpathogenic strain E. coli C600, PA2 produced Stx2a levels that were 2- to 12-fold higher than those observed during coculture with EDL933 and Sakai, respectively. Germfree mice cocolonized by PA2 and C600 showed greater kidney damage, increased Stx2a accumulation in feces, and more visible signs of disease than mice given PA2 or C600 alone. These data suggest one mechanism by which microorganisms associated with the colonic microbiota could enhance the virulence of E. coli O157:H7, particularly a subset of clade 8 strains.
authors.affiliation: Department of Food Science, Penn State University, University Park, Pennsylvania, USA.
authors.forename: Kakolie
authors.initials: K
authors.lastname: Goswami
authors.affiliation: Department of Food Science, Penn State University, University Park, Pennsylvania, USA.
authors.forename: Chun
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Food Science, Penn State University, University Park, Pennsylvania, USA.
authors.forename: Lingzi
authors.initials: L
authors.lastname: Xiaoli
authors.affiliation: Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Eaton
authors.affiliation: Department of Food Science, Penn State University, University Park, Pennsylvania, USA Center for Immunology and Infectious Disease, Penn State University, University Park, Pennsylvania, USA dudley@psu.edu.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Dudley
mesh_terms: D000818:Animals; D002417:Cattle; D018920:Coculture Techniques; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000254:growth & development*; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity*; D005260:Female; D005856:Germ-Free Life; D008297:Male; D051379:Mice; D022641:Shiga Toxin 2 / Q000096:biosynthesis*; D014774:Virulence
chemical_list: D022641:Shiga Toxin 2