CHARACTERIZATION OF FIMBRIAE PRODUCED BY ENTEROPATHOGENIC ESCHERICHIA-COLI

Enteropathogenic Escherichia coli (EPEC) express rope-like bundles of filaments, termed bundle-forming pili (BFP) (J. A. Giron, A. S. Y. Ho, and G. K. Schoolnik, Science 254:710-713, 1991). Expression of BFP is associated with localized adherence to HEp-2 cells and the presence o f the EPEC adherence factor plasmid. In this study, we describe the id entification of rod-like fimbriae and fibrillae expressed simultaneous ly on the bacterial surface of three prototype EPEC strains. Upon fimb rial extraction from EPEC B171 (O111:NM), three fimbrial subunits with masses of 16.5, 15.5, and 14.7 kDa were separated by sodium dodecyl s ulfate-polyacrylamide gel electrophoresis. Their N-terminal amino acid sequence showed homology with F9 and F7(2) fimbriae of uropathogenic E. coli and F1845 of diffuse-adhering E. coli, respectively. The mixtu re of fimbrial subunits (called FB171) exhibited mannose-resistant agg lutination of human erythrocytes only, and this activity was not inhib ited by alpha-D-Gal(1-4)-beta-Gal disaccharide or any other described receptor analogs for P, S, F, M, G, and Dr hemagglutinins of uropathog enic E. coli, which suggests a different receptor specificity. Hemaggl utination was inhibited by extracellular matrix glycoproteins, i.e., c ollagen type IV, laminin, and fibronectin, and to a lesser extent by g angliosides, fetuin, and asialofetuin. Scanning electron microscopic s tudies performed on clusters of bacteria adhering to HEp-2 cells revea led the presence of structures resembling BFP and rod-like fimbriae li nking bacteria to bacteria and bacteria to the eukaryotic cell membran e. We suggest a role of these surface appendages in the interaction of EPEC with eukaryotic cells as well as in the overall pathogenesis of intestinal disease caused by EPEC.