Involvement of the enteroaggregative Escherichia coli plasmid-encoded toxin in causing human intestinal damage

Enteroaggregative Escherichia coli (EAEC) strains have been shown to adhere to human intestinal tissue in an in vitro organ culture (IVOC) model, and certain strains manifest mucosal toxicity We have recently described the EA EC plasmid-encoded toxin (Pet), a member of a specific serine protease subc lass of the autotransporter proteins. When injected into rat ileal loops, P et both elicited fluid accumulation and had cytotoxic effects on the mucosa . Furthermore, the Pet protein caused rises in short circuit current from m t jejunal tissue mounted in a Ussing chamber and rounding of intestinal epi thelial cells in culture. We therefore hypothesized that the mucosal pathol ogy induced by EAEC strains in the IVOC model was related to expression of the Pet protein. Here, we have examined the effects of EAEC strain 042 and its isogenic pet mutant in the IVOC model. 042-infected colonic explants ex hibited dilation of crypt openings, increased cell rounding, development of prominent intercrypt crevices, and absence of epical mucus plugs. Colonic tissue incubated with the pet mutant exhibited significantly fewer mucosal abnormalities both subjectively and as quantitated morphometrically by meas urement of crypt aperture diameter. Mucosal effects were restored upon comp lementation of the pet mutation in trans. Interestingly, we found that the ability of 042 to damage T84 cells was not dependent upon Pet. The data sug gest that the Pet toxin is active on the human intestinal mucose but that E AEC may have other mechanisms of eliciting mucosal damage.