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.