Fimbria-like hemagglutinin of Escherichia coli O75 strains.

Fifteen strains of Escherichia coli O75 from human feces and patients with urinary tract infections were analyzed for their hemagglutinative properties, production of hemolysin and colicin, and plasmid contents. Fourteen strains produced type-1 fimbriae in broth culture. Nine of the strains agglutinated human P1 and p erythrocytes, i.e., possessed an X adhesin (X hemagglutinin). All but one of the X+ strains agglutinated human but not sheep or rabbit erythrocytes. Of the 15 strains, 4 had P fimbriae; one strain had both X hemagglutinin and P fimbriae. A coli-like structure was found by electron microscopy on the surface of the X+ strains. This structure was purified from two strains and characterized chemically and serologically. It was a protein consisting of subunits with an apparent molecular weight of 16,000. The amounts of hydrophobic amino acids in proteins purified from strains IH11033 and IH11128 were 35 and 39%, respectively. The amino acid content of the proteins was quite similar; only glutamine-glutamate and tyrosine contents were different. The radiolabeled protein bound to human erythrocytes, but it differed morphologically from typical E. coli fimbriae. Several methods showed the hemagglutinin, termed O75-X, to be serologically related in all the O75 X+ strains. The eight X+ O75:K5:H- strains had type-1 fimbriae and an identical outer membrane protein pattern, lacked P fimbriae and hemolytic activity, and are proposed to represent a clonal group.