Biologic activity of type I and type II Fusobacterium nucleatum isolates from clinically characterized sites.

Fusobacterium nucleatum is a microorganism commonly cultured from periodontal disease sites. F. nucleatum isolates (120) were obtained from subgingival plaque samples taken from 27 clinically characterized sites using a selective culture medium. All isolates were verified by morphology, Gram-stain reactions, oxygen tolerance and biochemical reactions. A total of eight clinical isolates and two typed strains were used for further evaluation. In this study, there was no relationship found between GI and probing depth or between probing depth and frequency of isolation of Type I or Type II F. nucleatum colonies. There was a significant increase in isolation of Type II colonies with a GI of 2 (P less than 0.0001). All isolates tested shared lines of identity by double diffusion in agar and displayed similar ability to hemagglutinate sheep erythrocytes and a reduction in this hemagglutination activity by previous exposure to 50 mM D-galactose. All isolates tested showed similar protein patterns as determined by polyacrylamide gel electrophoresis. By the methods used, no differences were detected between Type I and Type II F. nucleatum; however, there was a statistically significant increase in Type II isolates with increasing levels of gingivitis.