Detection of 2-keto-3-deoxyoctonate in endotoxins isolated from six reference strains of the Bacteroides fragilis group.

1. Endotoxins isolated from six serotype specific reference strains of the Bacteroides fragilis group were dephosphorylated by treatment with aqueous 50% hydrofluoric acid. 2. Mild acidic hydrolysis of the dephosphorylated endotoxins released 2-keto-3-deoxyaldonic acid, the presence of which was demonstrated by the colorimetric thiobarbituric acid assay (TBA). 3. Thin layer chromatography of the dephosphorylated lipopolysaccharide of B. fragilis IPL E 323 (serotype E2), after acidic hydrolysis, revealed a TBA-positive substance with the same Rf-value as authentical 2-keto-3-deoxyoctolusonic acid (KDO). 4. Quantification of 2-keto-3-deoxyoctonate-in the lipopolysaccharide of B. fragilis IPL E 323 by means of the TBA resulted in a KDO content of 15 nM mg-1 lipopolysaccharide.