Influence of in vitro propagation on the adhesive qualities of Streptococcus mutans isolated from saliva.

Streptococcus mutans from saliva of one test person were isolated on mitis/salivarius agar containing bacitracin and extra sucrose, and subcultured in vitro on trypticase soy broth with numerous transfers. Freshly isolated organisms and bacteria from selected subcultures were studied in adhesion tests using glass or dental zinc phosphate cement as substrate. Different bacterial isolates were used in separate experiments. Three different techniques were used; two based on radioactivity assays of adhering 3H-thymidine-labelled bacteria, and one based on visual counting. With all three techniques freshly isolated S. mutans adhered in significant numbers. It was consistently found that their ability to adhere decreased with the number of in vitro transfers. The results support the view that growth condition is an important factor governing the adhesive properties of oral bacteria.