The anticariogenic effect of xylitol on seven Streptococcus mutans strains

Introduction: Xylitol can affect caries-inducing bacteria; however, different Streptococcus mutans strains might respond differently. Aim: To investigate the effect of xylitol on biofilm formation and metabolic activity of seven S. mutans strains. Methods: Seven S. mutans strains (UA159, A32-2, NG8, 10449, UA130, LM7, and OMZ175) were inoculated into 96-well microtiter plates and were tested with various xylitol concentrations (0.0, 0.0016, 0.0031, 0.0063, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.4 and 0.8 g/mL) for inhibition of biofilm formation and bacterial metabolic activity by recording absorbance values. Lactate dehydrogenase and extracellular polysaccharide assays were conducted at 0.0, 0.1, 0.2, 0.4, and 0.8 g xylitol/mL. Data were analyzed by one-way analysis of variance, Tukey’s, paired t, and LSD tests at 0.05 significance level. Results: Xylitol produced a significant decrease in bacterial biofilm formation compared to controls at 0.4 g/mL, with almost complete lack of biofilm formation at 0.8 g/mL. This was consistent with metabolic activity which demonstrated a significant activity reduction occurring for all strains at 0.4 g/mL, and a complete lack of activity at 0.8 g/mL for all seven strains. There was a trend for lower LDH and EPS production with the increase in xylitol concentration especially with UA159, UA130, and NG8. Conclusion: Xylitol has a clear anticariogenic effect on S. mutans which was slightly different depending on the tested strain confirming that the benefit of xylitol might vary from one patient to another. The effect is more apparent at concentrations of 0.4 g/mL and higher