Characterization of adherent-invasive Escherichia coli isolated from pediatric patients with inflammatory bowel disease

Inflamm Bowel Dis. 2012 May;18(5):913-24. doi: 10.1002/ibd.21899. Epub 2011 Oct 12.


Background: Crohn's disease (CD) and ulcerative colitis (UC), known as inflammatory bowel diseases (IBD), are characterized by an abnormal immunological response to commensal bacteria colonizing intestinal lumen and mucosa. Among the latter, strains of adherent-invasive Escherichia coli (AIEC), capable of adhering to and invading epithelium, and to replicate in macrophages, have been described in CD adults. We aimed at identifying and characterizing AIEC strains in pediatric IBD.

Methods: In all, 24 CD children, 10 UC, and 23 controls were investigated. Mucosal biopsies, taken during colonoscopy, were analyzed for the presence of AIEC strains by an adhesive-invasive test. Protein expression of the specific AIEC receptor, the carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6), was evaluated by western blot and immunohistochemistry, while tumor necrosis factor alpha (TNF-α) and interleukin (IL)-8 mRNA expression was detected by real-time polymerase chain reaction (PCR), after bacterial infection. Transmission electron microscopy and trans-epithelial electric resistance assays were performed on biopsies to assess bacteria-induced morphological and functional epithelial alterations.

Results: Two bacterial strains, EC15 and EC10, were found to adhere and invade the Caco2 cell line, similar to the well-known AIEC strain LF82 (positive control): they upregulated CEACAM6, TNF-α, and IL-8 gene/protein expression, in vitro and in cultured intestinal mucosa; they could also survive inside macrophages and damage the epithelial barrier integrity. Lesions in the inflamed tissues were associated with bacterial infection.

Conclusions: This is the first study showing the presence of adhesive-invasive bacteria strains in the inflamed tissues of children with IBD. Collective features of these strains indicate that they belong to the AIEC spectrum, suggesting their possible role in disease pathogenesis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Animals
  • Antigens, CD / genetics
  • Antigens, CD / metabolism*
  • Bacterial Adhesion*
  • Blotting, Western
  • Case-Control Studies
  • Cell Adhesion Molecules / genetics
  • Cell Adhesion Molecules / metabolism*
  • Cells, Cultured
  • Child
  • Colitis, Ulcerative / immunology
  • Colitis, Ulcerative / microbiology*
  • Colitis, Ulcerative / pathology
  • Crohn Disease / immunology
  • Crohn Disease / microbiology*
  • Crohn Disease / pathology
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification*
  • Escherichia coli Infections / immunology
  • Escherichia coli Infections / microbiology*
  • Escherichia coli Infections / pathology
  • Female
  • Fluorescent Antibody Technique
  • GPI-Linked Proteins / genetics
  • GPI-Linked Proteins / metabolism
  • Humans
  • Immunoenzyme Techniques
  • Interleukin-8 / metabolism
  • Intestinal Mucosa / immunology
  • Intestinal Mucosa / microbiology
  • Macrophages / immunology
  • Macrophages / microbiology
  • Male
  • Mice
  • Organ Culture Techniques
  • RNA, Messenger / genetics
  • Real-Time Polymerase Chain Reaction
  • Tumor Necrosis Factor-alpha / pharmacology


  • Antigens, CD
  • CEACAM6 protein, human
  • Cell Adhesion Molecules
  • GPI-Linked Proteins
  • Interleukin-8
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha