Hemagglutination of human group A erythrocytes by enterotoxigenic Escherichia coli isolated from adults with diarrhea: correlation with colonization factor.

Enterotoxigenic Escherichia coli (ETEC) of several different serotypes isolated from adults with diarrhea and known to possess the colonization factor antigen (CFA) were found to cause mannose-resistant hemagglutination (HA) of human group A erythrocytes. CFA-negative E. coli isolated during the same study did not possess the mannose-resistant hemagglutinin, although some non-ETEC, CFA-negative isolates did exhibit mannose-sensitive HA activity. The mannoseresistant hemagglutinin of ETEC was found to possess many characteristics previously associated with CFA, which is a surface-associated fimbriate heatlabile antigen, and the functionally and morphologically similar K88 and K99 antigens of animal-specific ETEC. Mannose-resistant HA and CFA titers were maximal when ETEC cells were grown on an agar medium (CFA agar) composed primarily of 1% Casamino Acids and 0.15% yeast extract, pH 7.4. Neither CFA nor HA were produced at a growth temperature of 18 degrees C; HA was completely inhibited by pretreatment of CFA-positive cells with the anti-CFA serum. The mannose-resistant hemagglutinin was lost spontaneously and simultaneously with CFA when clinical ETEC isolates were passaged on artificial medium in the laboratory, indicating plasmid control of both entities. The mannose-resistant hemagglutinin of ETEC was shown to be thermolabile, i.e., sensitive to heating at 65 degrees C, as was the CFA. Also, there was correlation between possession of CFA, as detected serologically and by demonstration of biological activity (adherence in the infant rabbit small intestine), presence of CFA-type fimbriae, and the ability of various E. coli isolates to cause mannose-resistant HA of human group A erythrocytes. These results indicate that the mannose-resistant HA of ETEC is another manifestation of CFA.