title: The presence of the pAA plasmid in the German O104:H4 Shiga toxin type 2a (Stx2a)-producing enteroaggregative Escherichia coli strain promotes the translocation of Stx2a across an epithelial cell monolayer.
abstract: BACKGROUND
  A Shiga toxin type 2a (Stx2a)-producing enteroaggregative Escherichia coli (EAEC) strain of serotype O104:H4 caused a large outbreak in 2011 in northern Europe. Pathogenic mechanisms for this strain are unclear. We hypothesized that EAEC genes encoded on the pAA virulence plasmid promoted the translocation of Stx2a across the intestinal mucosa.
  
  
  METHODS
  We investigated the potential contribution of pAA by using mutants of Stx-EAEC strain C227-11, either cured of the pAA plasmid or deleted for individual known pAA-encoded virulence genes (ie, aggR, aggA, and sepA). The resulting mutants were tested for their ability to induce interleukin 8 (IL-8) secretion and translocation of Stx2a across a polarized colonic epithelial (T84 cell) monolayer.
  
  
  RESULTS
  We found that deletion of aggR or aggA significantly reduced bacterial adherence and (independently) translocation of Stx2a across the T84-cell monolayer. Moreover, deletion of aggR, aggA, sepA, or the Stx2a-encoding phage from C227-11 resulted in reduced secretion of IL-8 from the infected monolayer.
  
  
  CONCLUSIONS
  Our data suggest that the AggR-regulated aggregative adherence fimbriae I enhance inflammation and enable the outbreak strain to both adhere to epithelial cells and translocate Stx2a across the intestinal epithelium.
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine, Charlottesville.
authors.forename: Nadia
authors.initials: N
authors.lastname: Boisen
authors.affiliation: Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Hansen
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
authors.forename: Angela R
authors.initials: AR
authors.lastname: Melton-Celsa
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
authors.forename: Tonia
authors.initials: T
authors.lastname: Zangari
authors.affiliation: Technology for Industry and the Environment, Discovery-Science-Technology, RTI International, Research Triangle Park, North Carolina Biological and Nanoscale Systems, BioSciences Division, Oak Ridge National Laboratory, Tennessee.
authors.forename: Ninell Pollas
authors.initials: NP
authors.lastname: Mortensen
authors.affiliation: Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore.
authors.forename: James B
authors.initials: JB
authors.lastname: Kaper
authors.affiliation: Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
authors.forename: Alison D
authors.initials: AD
authors.lastname: O'Brien
authors.affiliation: Department of Pediatrics, University of Virginia School of Medicine, Charlottesville.
authors.forename: James P
authors.initials: JP
authors.lastname: Nataro
mesh_terms: D001422:Bacterial Adhesion; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism*; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005838:Genotype; D005858:Germany; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D010957:Plasmids; D021381:Protein Transport; D065288:Serogroup; D022641:Shiga Toxin 2 / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C088603:AggR protein, E coli; D029968:Escherichia coli Proteins; D016209:Interleukin-8; D022641:Shiga Toxin 2; D015534:Trans-Activators; D037521:Virulence Factors
keywords: O104:H4; Shiga toxin; diarrhea; enteroaggregative Escherichia coli (EAEC); pAA plasmid