Adhesion of Streptococcus mutans to Saliva-coated Hydroxyapatite formed in situ in Microtitre Plates

Abstract

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 saturation kinetics and there was an almost linear relationship between the number of adhering cells and the total input of cells. This is in accordance with results obtained by scanning electron microscopy. S. mutans adhered not only to the salivary pellicle but also to bound S. mutans cells. This phenomenon, referred to as homologous coadhesion, resulted in the formation of aggregates of S. mutans cells. Homologous coadhesion of S. mutans was enhanced significantly by saliva. The presence of bound bacterial cells of Streptococcus gordonii strain HG222 or Streptococcus sanguis strain Bart 10 on saliva-coated HA increased the number of adhering 5. mutans cells; the increase in the number of adhering S. mutans cells was most pronounced when the plates were precoated with the homologous 5. mutans strain HG982. Other oral streptococci, when bound to saliva-coated HA, decreased adhesion of S. mutans (Streptococcus oralis strains NY583 and ST26, Streptococcus mitis strain HG168) or had no effect on adhesion (S. sanguis strain Bart4, S. gordonii strain MCC272, 5. mitis strain ST3I). In conclusion, a new mechanism for accumulation of S. mutans on a saliva-coated HA surface has been proposed: the formation of aggregates of S. mutans cells.

Key Words:

• Streptococcus mutans
• adhesion
• hydroxyapatite
• microtitre plates
• salivary pellicle

Additional information

Notes on contributors

J. De Graaff

Joyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology.