title: Secretion of Alpha-Hemolysin by Escherichia coli Disrupts Tight Junctions in Ulcerative Colitis Patients.
abstract: OBJECTIVE
  The potential of Escherichia coli (E. coli) isolated from inflammatory bowel disease (IBD) patients to damage the integrity of the intestinal epithelium was investigated.
  
  
  METHODS
  E. coli strains isolated from patients with ulcerative colitis (UC) and healthy controls were tested for virulence capacity by molecular techniques and cytotoxic assays and transepithelial electric resistance (TER). E. coli isolate p19A was selected, and deletion mutants were created for alpha-hemolysin (α-hemolysin) (hly) clusters and cytotoxic necrotizing factor type 1 (cnf1). Probiotic E. coli Nissle and pathogenic E. coli LF82 were used as controls.
  
  
  RESULTS
  E. coli strains from patients with active UC completely disrupted epithelial cell tight junctions shortly after inoculation. These strains belong to phylogenetic group B2 and are all α-hemolysin positive. In contrast, probiotic E. coli Nissle, pathogenic E. coli LF82, four E. coli from patients with inactive UC and three E. coli strains from healthy controls did not disrupt tight junctions. E. coli p19A WT as well as cnf1, and single loci of hly mutants from cluster I and II were all able to damage Caco-2 (Heterogeneous human epithelial colorectal adenocarcinoma) cell tight junctions. However, this phenotype was lost in a mutant with knockout (Δ) of both hly loci (P<0.001).
  
  
  CONCLUSIONS
  UC-associated E. coli producing α-hemolysin can cause rapid loss of tight junction integrity in differentiated Caco-2 cell monolayers. This effect was abolished in a mutant unable to express α-hemolysin. These results suggest that high Hly expression may be a mechanism by which specific strains of E. coli pathobionts can contribute to epithelial barrier dysfunction and pathophysiology of disease in IBD.
authors.affiliation: Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.|Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Hengameh Chloé
authors.initials: HC
authors.lastname: Mirsepasi-Lauridsen
authors.affiliation: Host Microbe Interactomics Group, Wageningen University, Wageningen, The Netherlands.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Du
authors.affiliation: Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Struve
authors.affiliation: Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Godefroid
authors.initials: G
authors.lastname: Charbon
authors.affiliation: Host Microbe Interactomics Group, Wageningen University, Wageningen, The Netherlands.
authors.forename: Jurgen
authors.initials: J
authors.lastname: Karczewski
authors.affiliation: Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Karen Angeliki
authors.initials: KA
authors.lastname: Krogfelt
authors.affiliation: Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.|Department of Clinical Microbiology, Hvidovre University Hospital, Hvidovre, Denmark.|Department of Gastroenterology, Hvidovre University Hospital, Hvidovre, Denmark.
authors.forename: Andreas Munk
authors.initials: AM
authors.lastname: Petersen
authors.affiliation: Host Microbe Interactomics Group, Wageningen University, Wageningen, The Netherlands.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Wells