Indirect immunofluorescence for the detection of Bacteroides species in human dental pulp

In the present study, anaerobic culture was compared with indirect immunofluorescence for the detection of Bacteroides species in dental root canals. Microbiological samples were obtained from 30 freshly extracted human teeth as well as from 82 patients during the course of endodontic treatment. Each sample was anaerobically cultured. The total number of colony-forming units and number of black-pigmented colonies were enumerated. Black-pigmented colonies were subcultured and identified by Gram stain characteristics, cellular and colonial morphology, biochemical tests, and gas-liquid chromatography. Aliquots of the original sample were heat-fixed to glass slides and reacted with species-specific polyclonal antisera. The presence and proportion of Bacteroides gingivalis, Bacteroides intermedium, and Bacteroides endodontalis was then determined by immunofluorescence. Anaerobic culture demonstrated Bacteroides species in 27% of the bacteriological samples taken from extracted teeth and 20% of those from patient samples. By contrast, immunofluorescence detected Bacteroides species in 86% and in 49% of these same samples, respectively. B. intermedius was cultivable from 11% of the patient samples but identified in 43% of these same samples by immunofluorescence. B. gingivalis and B. endodontalis were cultivable from 4% and 1% of the patient samples, respectively, but detected by immunofluorescence in 15% and 16% of the samples. The sensitivity of immunofluorescence assays compared with anaerobic culture was 100% while specificity ranged from 64 to 89%. The data from this study indicate that indirect immunofluorescence can be used for the clinical detection of black-pigmented Bacteroides species infecting human dental pulp. * Supported in part by USPHS Grants DE 04898 and DE 07497. J. J. Z. is the recipient of a Research Career Development Award from the National Institute of Dental Research.