Serological studies of oral Bacteroides intermedius

Bacteroides intermedius is a gram negative, anaerobic microorganism associated with certain forms of human periodontal disease, including adult periodontitis and acute necrotizing ulcerative gingivitis. Previous studies have indicated the presence of two DNA homology groups which could be distinguished by analysis of protein patterns on polyacrylamide gel electrophoresis, as well as at least two serogroups within B. intermedius. The present study examined the serology of B. intermedius and determined the distribution of B. intermedius serogroups in clinical isolates and patient plaque samples. Serological reactions with unabsorbed rabbit antisera and antisera immunoabsorbed with B. intermedius strains demonstrated a previously unreported antigenic group within B. intermedius, serogroup C, in both immunodiffusion and immunofluorescence assays. Of 79 B. intermedius isolates from 68 subjects examined with specific antisera, 55% of the isolates and 52% of the subjects were categorized in serogroup C, 40% of the isolates and 46% of the subjects were in serogroup B, and 5% of the isolates and 6% of the subjects were in serogroup A. In 31 samples of subgingival dental plaque from adolescents known to harbor B. intermedius, 81% demonstrated serogroup B, 16% had serogroup A, and 3% had serogroup C.