Non-haemagglutinating fimbriae of enteropathogenic Escherichia coli (EPEC)

Two hundred and thirteen Escherichia coli strains originating in 12 countries were included in the study. Of these, 157 were classical enteropathogenic E. coli (EPEC) serotypes, 54 belonged to O138, O139 and O141 serogroups i.e. porcine edema disease strains and two strains were of serogroup O157 associated with haemorrhagic colitis. Surface hydrophobicity was determined by the salt aggregation test (SAT). Haemagglutination was assayed against erythrocytes of six animal species with strains grown under conditions known to promote expression of haemagglutinins. Sixty three EPEC strains were hydrophobic i.e. SAT value less than or equal to 0.1-1.6, and of these 15 did not haemagglutinate. Fimbriae were abundant on non-haemagglutinating strain 2178/58 (O26) when grown in nutrient broth. Fewer fimbriae per cell were present after growth on nutrient agar. Heat- and protease treatment reduces the surface hydrophobicity of EPEC strains. We propose that EPEC strains may carry a number of different surface proteins which determine binding to intestinal cells in a similar way as hydrophobic non-haemagglutinating fimbriae determine binding to rabbit intestinal brush borders, cf rabbit EPEC strain RDEC 1.