ADHESION OF STREPTOCOCCUS-MUTANS TO SALIVA-COATED HYDROXYAPATITE FORMED IN-SITU IN MICROTITRE PLATES

Adhesion of Streptococcus mutans to the salivary pellicle was studied in vitro by using microtitre plates coated in situ with hydroxyapatite (HA). Adhesion of S. mutans to these plates did not exhibit saturatio n kinetics and there was an almost linear relationship between the num ber of adhering cells and the total input of cells. This is in accorda nce with results obtained by scanning electron microscopy. S. mutans a dhered not only to the salivary pellicle but also to bound S. mutans c ells. This phenomenon, referred to as homologous coadhesion, resulted in the formation of aggregates of S. mutans cells. Homologous coadhesi on of S. mutans was enhanced significantly by saliva. The presence of bound bacterial cells of Streptococcus gordonii strain HG222 or Strept ococcus sanguis strain Bart10 on saliva-coated HA increased the number of adhering S. mutans cells; the increase in the number of adhering S . mutans cells was most pronounced when the plates were precoated with the homologous S. mutans strain HG982. Other oral streptococci, when bound to saliva-coated HA, decreased adhesion of S. mutans (Streptococ cus oralis strains NY583 and ST26, Streptococcus mitis strain HG168) o r had no effect on adhesion (S. sanguis strain Bart4, S. gordonii stra in MCC272, S. mitis strain ST31). In conclusion, a new mechanism for a ccumulation of S. mutans on a saliva-coated HA surface has been propos ed: the formation of aggregates of S. mutans cells.