Inhibition of phagocytosis of E. coli by B. fragilis group--an in vitro study.

Bacteriodes fragilis group can inhibit the phagocytosis and killing of co-existing aerobes. Forty six strains of B.fragilis group are tested for their ability to resist phagocytosis and inhibit the killing of indicator organism, E. coli by denoting the viable count. Among the species of B. fragilis group, the inhibitory index of the phagocytic system was the highest with B. fragilis followed by B. thetaiotamicron. None of the strains of B. fragilis group were phagocytosed or killed in this system. This property of resisting the phagocytosis and killing of E. coli by B. fragilis group might be the contributing factor towards their prevalence in mixed infections.