Quantitative determination of the serum antibody response to the capsular polysaccharide of Bacteroides fragilis subspecies fragilis in women with pelvic inflammatory disease.

The antibody response to the capsular polysaccharide of Bacteroides fragilis subspecies fragilis in women with acute pelvic inflammatory disease was quantitated using a sensitive radioactive antigen-binding assay. Antibody detected by this technique correlated highly with antibody measured by quantitative precipitin analysis (r = 0.99). Paired acute- and convalescent-phase sera obtained from women from whom B. fragilis subspecies fragilis was isolated by culdocentesis showed significantly greater changes in antibody concentration than corresponding sera obtained from women with gonococcal or nongonococcal pelvic inflammatory disease when B. fragilis subspecies fragilis was not isolated from the cul-de-sac. These data indicate that the steady state of immunity to this capsular antigen is perturbed in patients with acute nongonococcal pelvic inflammatory disease from whom this organism can be cultured. This finding may indicate that B. fragilis can play a significant role in acute pelvic inflammatory disease and can be involved early in the infectious process.