Methods:Rats were divided into groups. Group1 was fed a wildtype strain (DF2200rif), Group2 was fed a leukotoxin mutant strain Aa1700rif, and Group3 was not fed bacteria. Two and four weeks post inoculation the oral flora was sampled. Blood samples were taken pre-inoculation and at twelve weeks. Serum was tested for antibody to Aa by ELISA. X-rays were taken to assess for the alveolar bone loss. Colonization, antibody titer and bone loss were compared between groups by ANOVA and post-hoc testing.
Results: Colonization by the leukotoxin negative strain was not significantly different from the wild type strain. Only the wildtype strain fed rats had significant total bone loss (p< .02 versus control). When bone loss was analyzed by location, at site D (alveolar bone between molars2 and3) the wildtype fed group again showed a significant bone loss (p < .02 versus control). Although the leukotoxin mutant fed group shows more total bone loss and loss at site D than the control group, and less total bone loss and loss at site D than the the wildtype, the difference was not significant. Conclusion:. Leukotoxin may contribute to bone loss in the rat but other factors are necessary for the level of bone loss seen in the wildtype. Since the toxic effects of leukotoxin on leukocytes is limited to humans and old world monkeys—the lack of a strong effect of leukotoxins on bone loss in the rat is not unexpected. A more subtle effect of leukotoxin on bone loss in the rat in combination with other factors is not ruled out.