Hydrophobicity and adherence of oral streptococci after repeated subculture in vitro

Fresh isolates of Streptococcus mutans, Streptococcus sanguis, and Streptococcus salivarius from human dental plaque were all highly hydrophobic. After repeated subculture in vitro on blood agar, strains of S. mutans serotype c showed decreased hydrophobicity, whereas serotype d/g strains did not. Parallel to the decreased hydrophobicity in the serotype c strains, an impaired ability to adhere to hydroxyapatite was observed. A similar but less pronounced decrease in hydrophobicity in one S. sanguis strain resulted in a marked decrease in adherence to hydroxyapatite.