Ultrastructural study of adherence to and penetration of cultured cells by two invasive Escherichia coli strains isolated from infants with enteritis.

The adherence of invasive Escherichia coli strains 444-3 and 469-3 to human erythrocytes and to cultured HeLa and HEp-2 cells has been examined by electron microscopy. Bacteria elaborating type 1 fimbriae, glycocalyces , and nonfimbrial mannose-resistant hemagglutinins specific for human erythrocytes were identified in cultures of both strains, and each of these different bacterial surface components appeared to be involved in attachment of 444-3 and 469-3 to cultured epithelial cells or human erythrocytes (or to both). Both strains, which were isolated from infants with dysentery-like illness, penetrated cultured epithelial cells and existed within membrane-bounded intracellular vesicles. Mutants of 444-3 and 469-3 selected for deficiency in mannose-resistant hemagglutination did not adhere to or penetrate cultured cells. These ultrastructural studies demonstrate the complexity of the bacterial surface and show that E. coli strains 444-3 and 469-3 can elaborate several different adhesions , each of which could function to promote attachment to host intestinal epithelial cells. Mucosal invasion may also be an important virulence property of these strains.