Saliva-induced aggregation of oral streptococci and the influence of blood group reactive substances.

Aggregation of strains of Streptococcus rattus, Strep. mutans and Strep. salivarius by saliva from individuals of blood groups A, B and O was investigated. Blood group A salivas had a significantly higher aggregation activity with Strep. rattus than blood group B salivas (P less than 0.05). However, Strep. mutans and Strep. salivarius were better aggregated by blood group B saliva and this was significant for Strep. mutans (P less than 0.05). For all three strains, the variance within blood group O was too large to give significant differences with either blood group A or B. The blood group A-specific carbohydrate, N-acetyl-D-galactosamine, inhibited aggregation of Strep. rattus, but not of the other strains. The blood group B-specific carbohydrate, D-galactose, inhibited aggregation of Strep. mutans but not of Strep. rattus or Strep. salivarius. L-Fucose, specific for blood group O failed to inhibit aggregation of any of the three strains. These findings suggest that blood group-specific substances may be involved in bacterial aggregation.