wo polysaccharide complexes were extracted from Bacteroides fragilis ATCC-25285 andBacteroides fragilis CDC-14462 after treated with acids

heat

ethylenediamine tetraacetic acid andsodium deoxycholate etc. The facts that the two complexes have approxlmate amounts ofpolysaccharides and proteins

and that the nearly equal ratio of polysaccharides and proteins ineither of the complexes suggest that there may exist a structure in common. Both capsularpolysaccharide and lipidpolysaccharide may contribute to the saccharide composition of thecomplexes.In immunologial teste with antisera against B. fragilis and against the complexes

thetwo polysaccharide extracttions were showed to be the subspecies-specific antigens of B. fragilis

and statistically no difference in specificity was found between the two strains of B. fragilis

tested.As for other fractions presented in the extracting process

it was proved that they have nothing todo with the aiitigens of B. fragilis.These results indicate the possibility of preparing antisera withthe polysaccharide complexes and of establishing a much more specific immunological method fordetecting infections with B. fragilis

which will be subject to a forthcoming research.