Enterohemorrhagic Escherichia coli Colonization of Human Colonic Epithelium In Vitro and Ex Vivo

Abstract

Enterohemorrhagic Escherichia coli (EHEC) is an important foodborne pathogen causing gastroenteritis and more severe complications, such as hemorrhagic colitis and hemolytic uremic syndrome. Pathology is most pronounced in the colon, but to date there is no direct clinical evidence showing EHEC binding to the colonic epithelium in patients. In this study, we investigated EHEC adherence to the human colon by using in vitro organ culture (IVOC) of colonic biopsy samples and polarized T84 colon carcinoma cells. We show for the first time that EHEC colonizes human colonic biopsy samples by forming typical attaching and effacing (A/E) lesions which are dependent on EHEC type III secretion (T3S) and binding of the outer membrane protein intimin to the translocated intimin receptor (Tir). A/E lesion formation was dependent on oxygen levels and suppressed under oxygen-rich culture conditions routinely used for IVOC. In contrast, EHEC adherence to polarized T84 cells occurred independently of T3S and intimin and did not involve Tir translocation into the host cell membrane. Colonization of neither biopsy samples nor T84 cells was significantly affected by expression of Shiga toxins. Our study suggests that EHEC colonizes and forms stable A/E lesions on the human colon, which are likely to contribute to intestinal pathology during infection. Furthermore, care needs to be taken when using cell culture models, as they might not reflect the in vivo situation.

Enterotoxigenic and Enterohemorrhagic <i>Escherichia coli</i>: Survival and Modulation of Virulence in the Human Gastrointestinal Tract

“…Microaerobiosis also significantly reduced bacterial growth as well as Stx production and release into the medium, while Stx translocation across the epithelial monolayer was enhanced. The role of oxygen levels on modulation of EHEC virulence was further confirmed by Lewis et al [27] who showed in in vitro organ culture (IVOC) of human colonic biopsy samples that A/E lesion formation was dependent on oxygen levels. These lesions were suppressed under oxygenrich culture conditions routinely used for IVOC.…”

“…The main sites of colonization differ between the two pathogens: from the upper jejunum to the ileum for ETEC [23,24] and terminal ileum and colon for EHEC [25][26][27]. Notably, EHEC show a preferential tropism to the follicle-associated epithelium (FAE) of small intestinal Peyer's patches [25,28], which has not been described for ETEC.…”

The Surface Sensor NlpE of Enterohemorrhagic Escherichia coli Contributes to Regulation of the Type III Secretion System and Flagella by the Cpx Response to Adhesion

“…In this study, when EHEC cells bound to undifferentiated Caco-2 cells, expression of espA was increased NlpE dependently at 4 h postinfection. Since A/E lesions in EHEC cells formed between 4 and 6 h postinfection (45), the NlpE-dependent activation of the Cpx pathway in response to adherence might have been related to the increased virulence during EHEC infection. On the other hand, the Cpx pathway of E. coli K-12, which did not have LEE genes, was also activated NlpE dependently upon adhesion to hydrophobic glass beads after 1 h postadhesion (14).…”

The StcE metalloprotease of enterohaemorrhagicEscherichia colireduces the inner mucus layer and promotes adherence to human colonic epitheliumex vivo

“…Subsequently, the EHEC outer membrane protein intimin binds to translocated intimin receptor leading to intimate bacterial attachment and initiating further signalling events within the host cell, which ultimately result in actin polymerisation and pedestal formation (Stevens & Frankel, ). Although EHEC A/E lesions have not been observed clinically, ex vivo culture of human intestinal biopsies indicates EHEC A/E lesion formation in the distal small intestine and colon (Chong et al, ; Lewis, Cook, Tighe, & Schüller ).…”