The hydrophobicity of 'viridans' streptococci isolated from the human mouth

The hydrophobicity of human oral streptococci was measured with the hexadecane assay modified by the incorporation of polyethylene glycol 6000. Large variability in the hydrophobicity between cultures of some strains grown on different occasions was observed whereas other strains were less variable. The variation in hydrophobicity was significantly reduced by growing the cells in continuous culture in a chemostat under glucose-limiting conditions. The Streptococcus mutans strains used all had low hydrophobicity and the mean hydrophobicity of this species was significantly lower (P less than 0.05) than the mean hydrophobicity of Strep. salivarius, Strep. sanguis Type I and Strep. sanguis Type II strains. This finding supports the view that hydrophobicity is a contributing factor in the adhesion of viridans streptococci to oral surfaces.