New adhesive factor (antigen 8786) on a human enterotoxigenic Escherichia coli O117:H4 strain isolated in Africa

Abstract

An enterotoxigenic Escherichia coli strain, E. coli 8786, of serotype O117:H4 produced only heat-stable enterotoxin and gave mannose-resistant hemagglutination with human and bovine erythrocytes. The strain adhered to the brush border of human enterocytes and to enterocytelike cell line Caco-2. Adhesion inhibition assays using Caco-2 cells with different adhesive factor extracts showed that the adhesive factor of E. coli 8786 is different from colonization factor antigen I (CFA/I), CFA/II, CFA/III of Darfeuille et al. (A. Darfeuille, B. Lafeuille, B. Joly, and R. Cluzel, Ann. Microbiol. Inst. Pasteur 134A:53-64, 1983), CS6, and antigen 2230. A bacterial surface protein, designated antigen 8786, with a molecular mass of 16,300 Da was responsible for the adhesion to intestinal cells. It was immunologically different from previously described adhesive factors as determined by immunoblotting. Antigen 8786 was detected on the bacterial cell surface and appeared to be nonfimbrial. NH2-terminal analysis of antigen 8786 showed no homology with the previously described adhesive factors. Nevertheless, antigen 8786 is closely related to the NH2-terminal sequence of Salmonella enteritidis fimbrin. A hybridization experiment using a synthetic oligonucleotide probe based on the NH2-terminal amino acid sequence of antigen 8786 revealed that the coding region was located on a 70-MDa plasmid.