Haemagglutination patterns of diarrhoea-associated Escherichia coli strains in South Africa.

Using erythrocytes from six mammalian species, haemagglutination studies of 106 Escherichia coli isolates from infants with diarrhoea yielded fifteen different patterns. Although similar distribution patterns occurred between broth and agar grown cultures, individual strains often did not show identical patterns with the two methods of propagation. The complexity of patterns and medium-dependent variation of strains support the view that haemagglutination alone is not a suitable method for the demonstration of pili antigens. Furthermore, electron microscopy revealed pilus-like structures on the surface of only 21 out of 31 strains (66%) demonstrating positive haemagglutination. This finding is in accordance with the claim that surface antigens which are not derived from conventional pili may be responsible for attachment.