Endotoxic and Antigenic Fractions from the Cell Wall of Salmonella Enteritidis. Methods for Separation and Some Biologic Activities

Abstract

The toxic and antigenic roles of structural elements of Salmonella enteritidis have been investigated. Cell walls and protoplasm were prepared by mechanical agitation of deflagellated organisms in the Mickle apparatus followed by differential centrifugation. The separation procedure was controlled at each step by electron microscopy. Soluble endotoxin was released into the aqueous phase when suspensions in water of live cells or of unfixed cell walls were saturated with ethyl ether. Water soluble O-antigen of low toxicity was isolated by treatment of intact cells or cell walls with aqueous dioxane. The fractions were tested for toxic (lethal) action in mice, as flocculating antigens with O-antiserum, and as vaccines against expermental salmonellosis in mice. Toxicity, immunizing potency, and the substances which reacted serologically with O-antibody were present chiefly in the cell wall. The separated protoplasm retained only traces of these activities. The toxic aqueous ether extract (LD₅₀ for mice approximately 0.25 mg) also was an effective vaccine as well as a strong pyrogen and both a preparing and provoking agent in the local Shwartzman reaction. Aqueous dioxane extracts gave high flocculation titers and, although of substantially lower toxicity, afforded protection similar to that of endotoxins extracted from the same organism by aqueous ether or trichloracetic acid.