[Detection of Bacteroides fragilis enterotoxin from extraintestinal clinical isolates of B. fragilis group organisms].

A total of 300 extraintestinal clinical isolates of Bacteroides fragilis group organisms were assayed for enterotoxin using HT29/C1 cells. Of the 179 strains of B. fragilis, 36 (20.0%) were positive for cell culture assay, a positivity which was neutralized by anti-B. fragilis enterotoxin serum; all 36 strains were confirmed to be enterotoxigenic B. fragilis (ETBF). Among B. fragilis isolated from blood, 18 (31%) of 59 strains were ETBF while 18 (15.0%) of 120 strains isolated from non-blood specimens were ETBF (p < 0.05). None of the 121 strains of the B. fragilis group other than B. fragilis were positive for cell culture assay. These results demonstrated that isolation of ETBF from extraintestinal clinical specimens is not uncommon and that B. fragilis enterotoxin, a metalloprotease, may play a role as a pathogenic factor in blood stream infection and sepsis.