INVASION OF TISSUE-CULTURE CELLS BY DIARRHOEAGENIC STRAINS OF ESCHERICHIA-COLI WHICH LACK THE ENTEROINVASIVE INV GENE

Invasive Escherichia coli strains of certain serotypes invade by the s ame mechanism as the Shigella sp. It has been proposed that invasion o f epithelial cells by EPEC strains may also occur; this is a previousl y overlooked property. In the present study E. coli strains isolated f rom patients with diarrhoea or ulcerative colitis, lacking the inv pla smid mediating classical invasion, but hybridizing with probes for dif ferent adhesins, were analyzed for their ability to invade HeLa and Ca co-2 cells, The majority of strains invaded Caco-2 cells to a higher e xtent than HeLa cells, Adhesion to Caco-2 cells was a prerequisite for subsequent invasion of the cells but EAF, ene, EAgg and other known v irulence factors were not sufficient to mediate invasion. In 8/9 E. co li strains invasion was enhanced after growth under iron restriction. Growth during anaerobic conditions did not influence subsequent invasi on by E. coli strains whereas 6/9 strains had their invasive ability s ignificantly decreased after growth in the presence of 1% glucose. The invasive process was inhibited by mannose but not by lactose, fucose or galactose. Our data indicate that strains of E. coli may invade Cac o-2 cells by novel mechanisms which require adhesion to the cells but which differ from those of Salmonella sp., Yersinia sp., Shigella sp. and classical enteroinvasive E. coli.