Antibody response in thirteen patients with Bacteroides fragilis infections

13 patients with Bacteroides fragilis infections were studied for antibody response against the infecting strain using indirect immunofluorescence (IFL), passive hemagglutination (HA) and tube agglutination (TA). With indirect IFL significant titre changes in IgG were found in 12/13 cases, in IgA in 8/13 and in IgM in 4/13 cases. With passive HA significant titre changes were found in 11/13 cases and with TA in 6/11 cases. The rise in antibody titre was fast and persisted for a long time in most cases. Of the methods used the indirect IFL was the most convenient for clinical use.