Indirect fluorescent antibody procedure for the rapid detection and identification of Bacteroides and Fusobacterium in clinical specimens.

An indirect fluorescent antibody (IFA) technique was evaluated as a procedure for rapid detection and identification of members of the Bacteroidaceae. Antisera were prepared against 31 members of this family, including species of Bacteroides and Fusobacterium commonly isolated from human infections. The antisera had demonstrated species and/or subspecies specificity. Thirty clinical specimens were studied. Of 13 specimens yielding Bacteroidaceae, for which antisera were available, 23 were presumptively diagnosed by IFA to contain subspecies of B. fragilis and/or Fusobacterium species. Of 17 specimens yielding negative culture results, two were positive by IFA on direct smear. Frequently the in vivo morphology of cells detected in direct smears by this procedure closely mimicked that of cellular debris, tissue cells, and leukocytes. Polyvalent antisera pools facilitated use of the IFA procedure as a practical tool for rapid diagnosis of infections involving the Bacteroidaceae.