Purified lipopolysaccharides (LPS) from strains of Bacteroides, Fusobacterium and Veillonella were tested for endotoxic activity, utilizing the primary skin reaction and the Shwartzmam phenomena in rabbits. Comparisons were made to Salmonella LPS, Each LPS preparation produced the primary skin reaction in a typical dose-response fashion. Skin sites injected with 400 \ig of Fusobacterium LPS often produced necrotic lesions. In the comparisons made between the skin lesion doses (SLDjj) of the Veillonella LPS and the Salmonella LPS, the difference was either non-significant or the Salmonella LPS was only slightly more active (P < 0.02), LPS from the Fusobacterium and the Bacteroides were significantly less toxic than the Salmonella LPS (P < 0,005), All LPS preparations did prepare the skin for the local and the specific organs for the generalized Shwartzman reaction. The toxicity of the Bacteroides LPS was, however, very low in the local reactioti (P < 0,005). For all LPS preparations the sensitivity of the primary skin test (SLDsj) was superior to the local Schwartzman reaction {SPD^o) (P < 0,005).Twenty-four hours after challenge for the generalized Shwartzman reaction, extensive fibrin thrombi in the capillaries of the renal glomemli were found, as well as thrombi containing necrotic blood cells, both in the veins of the liver and in the arteries of the lungs.The high endotoxic activity of the Fusobacterium and the Yeillonella LPS may reflect a similarity between their lipid A and that of the Salmonella LPS, rate the O-antigens of the bacteria atid a

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Lipopolysaccharides (LPS) extracted from strains of Bacteroides fragilis, Bacteroides melaninogenicus and Bacteroides oralis with phenol‐water, trichloroacetic acid, EDTA or liquid phenolchloroform‐petroleum ether (PCP) and isolated by ultracentrifugation, varied considerably in their quantitative chemical composition. Negligible yields of LPS were obtained by PCP‐extraction. All preparations were more or less serologically active. All methods (except PCP) extracted the same O‐antigenic determinants from B. fragilis. Endotoxic activity, as measured by primary skin inflammations in rabbits, was low but was present in all preparations. Proteins (and/or lipoproteins) co‐precipitated with LPS in the ultracentrifuge.

Phenol‐water extracted lipopolysaccharides (LPS) from Veillonella, Fusobacterium nucleatum, Bacteroides fragilis and Bacteroides melaninogenicus were lethal for mice and 11‐days‐old chick embryos, pyrogenic in rabbits, and gelated Limulus amoebocyte lysate. Mouse lethality was considerably enhanced by actinomycin‐D. In all test systems the endotoxin activity of Veillonella and Fusobacterium LPS was comparable to that of LPS from Salmonella enteritidis, which was included as a reference endotoxin. The endotoxicity of the Bacteroides LPS was very low. While nanograms of the Veillonella and Fusobacterium LPS killed the chick embryos and gelated the Limulus lysates, microgram amounts of the Bacteroides LPS were needed to give positive reaction in the same test systems. As much as 74 μg of the most active B. fragilis LPS were required to give a typical biphasic fever response in rabbits. A significant correlation was found between all test results (r = 0.90‐0.98, p < 0.001).