CONICET | Buscador de Institutos y Recursos Humanos

Introduction. Enterohemorragic Escherichia coli (EHEC), and among themthe prototypic serotype O157:H7, are zoonotic bacteria responsible forintestinal disease and hemolytic uremic syndrome (HUS), a serious systemiccomplication which particularly affects children. The main virulence factor ofEHEC is the Shiga toxin 2 (Stx2). The aim of the present study was to examinethe physiological and morphological effects of EHEC O157:H7 on human colonicmucosa in the presence of colloidal bismuth hydroxide (GBiOH). Methods. We have used a dose of 3.107 CFU/mlobtained from exponential phase EHEC O157:H7 strain 125/99 (stx2+) belonging tothe hypervirulent clade 8 isolated from a HUS case. Bacteria (200 µl) added tothe mucosal side of the colonic mucosa mounted as a diaphragm in a Ussing chamberrecorded automatically by an electro-optical device Results and Discussion. EHEC O157:H7 strain 125/99 causedan inhibition of the normal water absorption (Jw= 0.11 ± 0.02 vs 0.04 ± 0.01 µl/min.cm2, n= 6, p<0.05).Histopathological analysis at the end of experiment revealed destruction of theupper third of the colonic mucosa and areas of hemorrhagic damage. Thepre-incubation of colonic mucosa with GBiOH (0.4-0.8 mg/ml) for 30 min significantlyprevented the inhibition of water absorption and the microscopic alterations. Plaquecounting of the bacteria in the mucosal side of Ussing chamber showed a similarCFU/ml after and before addition of 0.8 mg/ml GBIOH.Vero cells cytotoxicity assay showed a significant Stx2 activity in the filteredsupernatants when colonic mucosa pre-incubated with 0.4 mg/mL GBiOH and then exposed to EHEC. The Stx2 activity wasreduced when the GBIOH concentration was 0.8 mg/ml. Implications. These results indicate that theinhibitory effect of GBiOH on human intestinal action of EHEC O157:H7 include adirect protection of colonic mucosa and inactivation of bacterial factorsresponsible for Stx2 production.