Detection of Bacteroides infection by counter immunoelectrophoresis test

The counterimmunoelectrophoresis (CIE) test using sonicated antigens of Bacteroides fragilis NCTC 2553 and a B. asaccharolyticus strain, standardised in the laboratory yielded a negative result in the 50 normal sera tested, while it was positive in 24 of 34 (71%) patients with infection due to black pigmented bacteroides and in 10 of 15 (67%) with B. fragilis infection. The microagglutination test (MAT) done in parallel showed a positivity of only 44 and 40 per cent respectively. The CIE test done with B. asaccharolyticus antigen was negative in 87 per cent of patients with infection due to B. fragilis whereas MAT showed cross reactivity to a greater extent.