Detection of specific bacterial antigen in urine of patients infected with Bacteroides fragilis

An indirect enzyme-linked immunosorbent assay was developed to detect specific Bacteroides fragilis antigen(s) in human urine. Specimens collected within 72 hr of a positive culture were centrifuged, dialyzed, and treated with Tween 20, polyethylene glycol, and bovine serum albumin. Goat hyperimmune γ-globulin to B. fragilis strain ATCC 23745 was added and incubated, and supernatants were tested for antibody activity to polysaccharide-protein antigen of the same organism. Mean ± SD results, reported as percentage inhibition of control values and interpreted blindly, were as follows: 29 normal subjects, 9.8% ± 6.0%; 22 patients with Enterobacteriaceae bacteremia, 6.0% ± 5.1%; six patients with nonbacteremic infections due to B. fragilis, 22.3% ± 10.3%; and nine patients with B. fragilis bacteremia, 28.7% ± 10.2%. Three of six nonbacteremic patients and eight of nine bacteremic patients yielded values > 2 SD of control values. None of 22 patients with Enterobacteriaceae bacteremia was falsely positive (specificity, 100%).