Physical and Chemical Analysis of Endotoxin from Salmonella Enteritidis

Some physical and chemical properties of the aqueous ether extract from Salmonella enteritidis (grown in synthetic medium) possessing the biologic properties of a Boivin-type antigen are described. The crude extract refined by dialysis or precipitation with ethanol contained polysaccharide and protein in proportions typical for endotoxin compounds, but had an exceptionally low lipid content. The polysaccharide contained rhamnose, mannose, galactose, and glucose. Major portions of the protein moiety could be removed without alteration of toxic and antigenic activities. Nonhydrolytic removal of at least one-half of firmly bound lipid was achieved. Preparations containing only 1–4% bound lipid were as toxic as Salmonella endotoxins containing 15–30% bound lipid and induced in mice specific resistance to challenge with virulent Salmonella enteritidis, whereas a fraction comparable to Westphal's “lipid A” was inactive. Sedimentation studies demonstrated the complex behavior of the endotoxin in solution. Fractions with reduced lipid content were homogeneous and had low sedimentation rates.