The association of haemagglutination and adhesion with lipopolysaccharide of Shigella dysenteriae serotype 1.

In this study the ability of strains of Shigella dysenteriae serotype 1 to agglutinate mammalian erythrocytes is attributed to the polysaccharide fraction of bacterial-cell lipopolysaccharide (LPS). LPS obtained from a rough, mutant strain of S. dysenteriae serotype 1, lacking the O-antigen polysaccharide side-chain, did not agglutinate erythrocytes, clearly demonstrating a link between O-antigen polysaccharides and haemagglutinating activity (HA). Strains of S. dysenteriae serotype 1 adhered well to cultured Henle Intestinal 407 cells, whereas rough strains adhered poorly. Pre-treatment of bacteria with LPS-specific antisera inhibited both HA and binding to cultured human-intestinal cells. The contribution of the polysaccharide side-chain and its associated HA--which appear to facilitate binding to cultured cells--to bacterial attachment to colonocytes and to the pathogenesis of shigellosis in vivo needs to be confirmed in animal studies.