Comparison of serological reactions of typed Fusobacterium nucleatum strains with those of isolates from humans, canines, and a Macaca mulatta monkey

In the present study, we compared typed F. nucleatum strains with isolates from various human periodontal diseases, canines, and a Macaca mulatta monkey. All isolates displayed biochemical reactions similar to those of the typed strains in the API 20A system (Analytab Products, Plainville, N.Y.). The human and monkey isolates displayed both type I and type II colonial morphologies on crystal violet erythromycin agar, whereas the canine isolates displayed only type I. Antigen preparations of the human isolates, typed strains, and two of the monkey strains shared lines of identity in immunodiffusion testing. An enzyme-linked immunosorbent assay in which rabbit anti-F. nucleatum and human sera were used revealed that the human and monkey isolates, when used as antigens, allowed the detection of similar degrees of antibody activity; however, no activity was observed with the canine isolates. None of the canine isolates displayed the characteristic hemagglutination of sheep erythrocytes demonstrated by the human and monkey strains. These results suggest that F. nucleatum isolates from various human periodontal diseases share antigenic determinants. Also, differences were observed in F. nucleatum isolates from canines when compared with human and monkey strains. These findings are important when considering the immunopathological mechanisms involved in human periodontal diseases and when comparing animal model systems with naturally occurring disease in humans.