BIOLOGICAL-ACTIVITY OF BACTEROIDES LIPOPOLYSACCHARIDE - REAPPRAISAL

Lipopolysaccharide (LPS) was extracted from six species of Bacteroides by the phenol/water, petroleum/chloroform/phenol, and Triton/magnesiu m methods. Yields and chemical analysis demonstrated that the products were different. Biological activity (endotoxicity) was assessed by th e limulus amebocyte lysate (LAL) assay, induction of tumor necrosis fa ctor (TNF) from human mononuclear leukocytes, and a lethality model wi th galactosamine-sensitized mice. Results showed that endotoxicity var ied greatly depending on the species and the extraction method. LPS pr epared by the phenol/water method was most endotoxic and that from Bac teroides fragilis had the greatest activity, Compared with Escherichia coli LPS, the phenol/water extract of B. fragilis was sevenfold more active in the LAL assay and marginally less active (five- to seven-fol d) in the bioassay for TNF induction. However, when B. fragilis LPS wa s added to E. coli LPS, the induction of TNF was inhibited. In the mou se model, B. fragilis LPS was 5,000-fold less toxic. If the gastrointe stinal tract is the source of the endotoxin in patients with systemic inflammatory response syndrome, then the obligately anaerobic Bacteroi des species, which outnumber the facultative species such as E. coli b y 1,000-fold, should not be overlooked.