Characterization of endotoxin from Fusobacterium necrophorum

Abstract

Endotoxic lipopolysaccharide (LPS) was obtained from phenol water extraction of cell walls prepared from mass cultivated Fusobacterium necrophorum. The LPS was relatively free of nucleic acids and low in protein, and constituted about 4% of the cell walls. Upon acid hydrolysis, some of the components detected were hexosamines (7.0%), neutral and reducing sugars (50.5%), heptose (6.4%), 2 keto 3 deoxyoctonate (0.8%), lipid A (21.0%), and phosphorus (1.7%). Under electron microscopy the LPS appeared mainly as ribbon like trilaminar structures, and upon chemical treatment it displayed a behavior resembling that reported in certain enterobacterial LPS. The LPS was lethal to mice, 11 day old chicken embryos, and rabbits. Endotoxicity in mice was enhanced at least 1,380 fold by the addition of 12.5 μg of actinomycin D. Induced tolerance to lethal effect of the endotoxin and rapidly acquired resistance to infection by F. necrophorum viable cells were also demonstrated in mice. The endotoxin produced both localized and generalized Shwarzman reactions as well as biphasic pyrogenic responses in rabbits. These results firmly establish the presence of a classical endotoxin in F. necrophorum, thus providing strong support to the authors' recent suggestion that cell wall associated components may contribute significantly to the pathogenicity of F. necrophorum.