Binding of enterotoxigenic Escherichia coli expressing different colonization factors to tissue-cultured Caco-2 cells and to isolated human enterocytes

The binding of ETEC strains expressing different colonization factors to the human enterocyte-like cell line Caco-2 and to isolated human enterocytes were determined. Strains expressing CFA/I, CS2, CS4+CS6, C55+CS6, CS7, CFA/III+CS6 and PCFO166 adhered well to both types of cells whereas bacteria producing CS1, CS6 only, or CS17 did not adhere to either Caco-2 cells or to jejunal human enterocytes, suggesting that similar binding structures are present in both cell types. However, in some instances, binding of bacteria to the two types of cells differed, e.g. bacteria expressing CS3 or PCFO9 bound well to human enterocytes but not to Caco-2 cells. Conversely, bacteria producing PCFO20 or PCFO159 only adhered to Caco-2 cells and not to jejunal enterocytes. With few exceptions, this inability to bind to human enterocytes was the same for cells from all parts of the small intestine. This study contradicts previous reports suggesting that the binding structures of Caco- 2 cells are identical to those of human enterocytes.