Radioimmunoassay for Bacteroides fragilis infections

Radioimmunoassay methods were evaluated for immunoglobulin G and immunoglobulin M antibodies against Bacteroides fragilis antigen. Of 12 serum samples from patients with B. fragilis infections, 9 had higher concentrations of immunoglobulin G antibodies than any from 11 control subjects. Of 9 serum samples from infected patients, 6 had higher concentrations of immunoglobulin M than any from control subjects. Six serum samples from patients with Escherichia coli bacteremia did not contain elevated concentrations of immunoglobulin G or immunoglobulin M antibodies against B. fragilis antigen.