Effect of Xylitol on the Growth and Metabolism of Streptococcus mutans

Abstract

Cells of cariogenic Streptococcus mutans (Ingbritt) were maintained and grown in a Trypticase-Phytone-based medium which contained either glucose, xylitol or their combinations as the added carbohydrate. 2.5% xylitol retarded the growth of the cells in the presence of 0.25% glucose, but during 2.5 months adaptive period the cells were able to tolerate the presence of xylitol. However, no evidence was obtained in 10 months of a possible adaptation to metabolize xylitol. Instead, indications of an adaptation to metabolize other compounds (for example, amino acids or peptides) were obtained. Xylitol had no strong effect on the uptake of glucose by the cells which were adapted to tolerate this polyol. 3% xylitol inhibited by 40–50% the activity of dextran-hydrolyzing extracellular enzyme(s) in the growth medium of the above cells in the conditions used. The extracellular polysaccharide-forming activity by the cells was increased 60–80% by low concentrations of xylitol (up to 55 mg/ml growth medium). Higher concentrations were inhibitory.