APPLICATION OF INDIRECT IMMUNOFLUORESCENCE TO DETECTION OF DIENTAMOEBA-FRAGILIS TROPHOZOITES IN FECAL SPECIMENS

An indirect fluorescent-antibody (IFA) assay was carried out to examin e for the presence of Dientamoeba fragilis trophozoites in preserved f ecal specimens. Antiserum to D. fragilis trophozoites was raised in a rabbit with a dixenic culture of D. fragilis (ATCC 30948) from the Ame rican type Culture Collection. After absorption with Klebsiella pneumo niae and Bacteroides vulgatus, the immune rabbit serum was used for ex amination by the IFA assay. A total of 155 clinical samples were teste d: 42 with no parasites, 9 with D. fragilis, and 104 with other parasi tes. The IFA assay identified seven D. fragilis organisms. Two specime ns with doubtful IFA assay readings showed very scanty amounts of D. f ragilis trophozoites on stained smears. There were no false-positive I FA assay readings. The IFA assay appeared to be a promising method bec ause of its speed in screening. The specificity of the IFA assay indic ates that other diagnostic tests such as an enzyme-linked immunosorben t assay could be developed to identify D. fragilis antigens in fecal s pecimens.