Adherence of enteroaggregative Escherichia coli to the ileal and colonic mucosa: an in vitro study utilizing the scanning electron microscopy

Abstract

-Context -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. Conclusion -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.

Pathogenesis of Human Enterovirulent Bacteria: Lessons from Cultured, Fully Differentiated Human Colon Cancer Cell Lines

“…This IVOC system has been used mainly to study the mechanisms of virulence of ETEC (839), EPEC (840)(841)(842)(843)(844)(845)(846)(847)(848)(849)(850)(851), EHEC (852)(853)(854)(855)(856)(857), EAEC (507,858), and Salmonella (392) and the action of Stx toxins (641). Other IVOCs have been used for studies on C. jejuni (859), EPEC (692,860,861), EAEC (645,(862)(863)(864), and Shigella (865) pathogenesis. Moreover, IVOCs from colonic biopsy specimens from CD patients have been used to show the adhesion of AIEC (444,866).…”

Ex Vivo Model of Rabbit Intestinal Epithelium Applied to the Study of Colonization by Enteroaggregative Escherichia Coli

“…The study of EAEC in several models, such as in the in vitro/in vivo assays in animals (22,23) , in the in vitro organ culture in cellular lines (1,9,18) and with human intestinal fragments (1,2,10,15,18,23) has been widely used by more faithfully mimic the EAEC action in the host.…”

“…Most of the knowledge about the interactions of bacteria and intestinal organs has been obtained from studies with human biopsies collected during surgical intervention or from samples obtained from elderly individuals at autopsy (8) . In order to elu-cidate the mechanisms of EAEC pathogenesis, models of study in organ culture in vitro (IVOC) from intestinal fragments from different portions of the small or/and large intestines of pediatric patients (1,2,10,18,23) and of adults (2,15,23) have been developed. Here we propose a more feasible animal study model in order to apply our understanding on the pathogenesis mechanism of EAEC strains.…”

Epidemiology and Clinical Manifestations of Enteroaggregative Escherichia coli

“…2). Knowledge of the stages of EAEC pathogenicity has been obtained from studies of in vitro cell cultures, animal models, and patients infected with EAEC (10,(13)(14)(15)(16)(17).…”

“…Persistent diarrhea is most frequently reported in children aged Յ1 year (32, 35, 87, 88). The site of colonization is believed to include the colon and the terminal ileum (10,14,55,89). The incubation time ranges from 8 h to 52 h (78,(90)(91)(92).…”