Hemagglutinating properties of enteroaggregative Escherichia coli

Many intestinal bacterial pathogens possess hemagglutinating properties, which are indicative of their adhesive properties to the intestinal mucosal surface. To understand the bacteria-mucosa interaction, 41 strains of enteroaggregative Escherichia coli (EAggEC), a recently described category of diarrheagenic E. coli, isolated mostly from children with diarrhea in Bangladesh, India, Thailand, Central America, and South America were screened for mannose-sensitive hemagglutination and mannose-resistant hemagglutination of erythrocytes from humans, rats, mice, sheep, cattle, and rabbits. Some strains demonstrated mannose-sensitive hemagglutination of erythrocytes. Most isolates showed mannose-resistant hemagglutination of erythrocytes from all species except rabbits. The hemagglutination patterns could be classified into 18 groups. Studies with three selected isolates suggested that hemagglutinins are cell bound and are protein in nature. On the basis of the pattern of inhibition of hemagglutination by various chemicals, 39 isolates were classified into 19 groups. Hemagglutinations of many isolates were inhibited by sialic acid-containing compounds, suggesting that these compounds may be the receptors for these organisms on erythrocytes and possibly on the intestinal mucosa. These data indicate that strains of EAggEC are a heterogeneous group of organisms with different types of hemagglutinins or adhesins for the intestinal mucosal surface. Also, the adhesion characteristics of EAggEC strains may be too complex to be assessed by simple hemagglutination tests.