Effect of Microbial Interactions on In Vitro Plaque Formation by Streptococcus mutans

Eight non-plaque-forming oral organisms were grown in paired mixed cultures with Streptococcus mutans in an in vitro plaque assay system. The amount of plaque that formed was compared with that formed by pure cultures of S mutans. Four organisms had no effect on the total amount of plaque that formed, three organisms caused decided inhibitions, and one organism greatly increased total plaque formation.