Xylitol is a sugar alcohol frequently used in the prevention of dental caries. However, the mechanism of action of xylitol on mutans streptococci is still unclear. This study evaluated the ultrastructural cellular changes in Streptococcus mutans and Streptococcus sobrinus after xylitol treatment.

S. mutans ATCC 25175 and S. sobrinus ATCC 33478 were grown separately in BHI medium plus 0.2% sucrose at 37°C under microaerophilic conditions overnight. Then, planktonic cells were harvested by centrifugation, resuspended in a fresh medium and incubated with either 0.2% glucose or 0.2% xylitol solutions for 2 hours. To prepare bacterial cells for the evaluation of morphology of cellular walls and polysaccharide capsules, cultures were subsequently fixed with 2.5% glutaraldehyde, stained with ruthenium red, post-fixed with 1% osmium tetroxide, dehydrated in acetone, embedded in Epon LX112 and analyzed by a transmission electron microscopy.

Bacterial cells incubated with glucose showed welldefined cellular walls and well-stained cytoplasmic membrane. Unlike, xylitol yielded diffuse cellular wall and irregular polysaccharide capsules in both microorganisms.

Low xylitol concentrations also can induce cellular damage to both S. mutans and S. sobrinus. Further studies are needed to provide more evidence on the anticariogenic effect of xylitol.

Pereira AFF, Silva TC, Machado MAAM, Buzalaf MAR. Low Xylitol Concentration induces Ultrastructural Cellular Changes in Streptococcus mutans and Streptococcus sobrinus. Int J Experiment Dent Sci 2015;4(1):1-3.