Characterization of an invasive phenotype associated with enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAggEc) strains are associated with persistent diarrhea in children in the developing world and exhibit a classic aggregative phenotype. We have demonstrated that EAggEc strains isolated from children with persistent diarrhea in Brazil, Bangladesh, and Pakistan also have the potential to be internalized by HeLa cells in the gentamicin protection assay. We have confirmed this phenomenon with transmission electron micrographs of bacteria engulfed by HeLa cells. We examined the mechanisms by which this process occurs. Staurosporine inhibited internalization of EAggEc strain 162 by 50% at a concentration of 0.1 microM. Genistein inhibited internalization of this same organism by 50% at a concentration of 50 microM. Cytochalasin D inhibited internalization by 50% at a concentration of 1 microgram/ml. Staurosporine, genistein, and cytochalasin D inhibited the internalization of EAggEc strain 162 by HeLa cells in a dose-dependent manner. These data suggest that active cell processes such as signal transduction by protein kinase and/or tyrosine kinase may be involved in the internalization of EAggEc strain 162 by HeLa cells and that actin filaments and cytoskeletal structure may be important for this process.