title: Adherence of enteroaggregative Escherichia coli to the ileal and colonic mucosa: an in vitro study utilizing the scanning electron microscopy.
abstract: BACKGROUND
  Enteroaggregative Escherichia coli strains have been associated with persistent diarrhea in several developing countries. In vivo procedures with animal models, in vitro assays with cellular lines and in vitro organ culture with intestinal fragments have been utilized to study these bacteria and their pathogenicity.
  
  
  OBJECTIVE
  The present experimental research assessed the pathogenic interactions of three enteroaggregative Escherichia coli strains, using the in vitro organ culture, in order to show the adherence to different regions of both, the ileal and the colonic mucosa and demonstrate possible mechanisms that could have the participation in the prolongation of diarrheiogenic process.
  
  
  METHODS
  This study used intestinal fragments from terminal ileum and colon that were excised from pediatric patients undergoing intestinal surgeries and from adult patients that underwent to colonoscopic procedures. Each strain was tested with three intestinal fragments for each region. Tissue was fixed for scanning electron microscopic analysis.
  
  
  RESULTS
  These bacteria colonized ileal and colonic mucosa in the typical stacked-brick configuration in the ileum and colon. In both regions, the strains were seen over a great amount of mucus and sometimes over the intact epithelium. In some regions, there is a probable evidence of effacement of the microvilli. It was possible to see adhered to the intestinal surface, bacteria fimbrial structures that could be responsible for the adherence process.
  
  
  CONCLUSIONS
  In order to cause diarrhea, enteroaggregative Escherichia coli strains adhere to the intestinal mucosa, create a mucoid biofilm on the small bowel surface that could justify the digestive-absorptive abnormalities and consequently, prolonging the diarrhea.
authors.affiliation: Division of Pediatric Gastroenterology, UNIFESP-EPM, São Paulo, SP, Brazil.
authors.forename: Jacy Alves Braga de
authors.initials: JA
authors.lastname: Andrade
authors.forename: Edna
authors.initials: E
authors.lastname: Freymüller
authors.forename: Ulysses
authors.initials: U
authors.lastname: Fagundes-Neto
mesh_terms: D000328:Adult; D001422:Bacterial Adhesion; D002648:Child; D003106:Colon / Q000382:microbiology* / Q000648:ultrastructure; D003967:Diarrhea / Q000382:microbiology; D004926:Escherichia coli / Q000472:pathogenicity* / Q000648:ultrastructure; D006801:Humans; D007082:Ileum / Q000382:microbiology* / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000382:microbiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning