[Induction of fluoride-resistant mutant of S. mutans and the measurement of its acidogenesis in vitro]

Abstract

Objective: To induce fluoride-resistant mutant of S. mutans in vitro and find out the differences of cariogenicity between them.

Methods: Fluoride-resistant strain Ingbritt-FR was obtained by subculturing S. mutans Ingbritt to TSA and TSB containing different concentrations of fluoride. Lactic production and terminal pH of media were measured by gas chromatography method.

Results: 1. The stable fluoride-resistant mutant of S. mutans Ingbritt had been induced successfully in vitro; 2. Lactic production of Ingbritt-FR was significantly more than its parent strain at various initial pH values with 0.5 and 5.0 mmol/L fluoride whereas when no fluoride existed, there were two situations: the acid production was more than S. mutans Ingbritt at initial pH above 5.0 while the result was opposite when pH was 5.0 and below.

Conclusion: The fluoride-resistant strain Ingbritt-FR had a stronger cariogenic potential than its parent strain S. mutans Ingbritt in physiological plaques.