Endotoxic activities of lipopolysaccharides of microorganisms isolated from an infected root canal in Macaca cynomolgus.

Lipopolysaccharides (LPS) prepared from a strain of Bacteroides oralis, a strain of Fusobacterium necrophorum, and a strain of F. nucleatum, all isolated from an infected root canal in monkey (Macaca cynomolgus), were examined for endotoxic activities using primary skin reactions in rabbits and induction of leukocyte chemotaxis in rats. LPS of B. oralis showed considerably lower ability to cause skin inflammation than LPS of the fusobacteria. However, the leukotactic effect of the LPS preparations as determined by the wound chamber method in rats was approximately of the same proportion. In both tests the reactions were compared with those of commercial LPS of Salmonella typhi. This study shows that endotoxic LPS can be isolated from oral Gram-negative bacteria, which have infected the root canal. Therefore LPS may play a role in the development and maintenance of chronic inflammation of the periapical tissues.