Methods: Cultures of Streptococcus mutans ATCC 33478 and Streptococcus sobrinus ATCC 25175 were grown in Brain Heart Infusion Medium (BHI; Difco Co.) in 5% CO2 at 37oC overnight (OD: 0.3-0.4, 650 nm wavelength). After that, cultures were harvested by centrifugation and re-suspended in fresh medium. A volume of 1 mL of cell suspensions were exposed one time to 10 μL of sterile basic medium containing glucose (control group) or 20% xylitol (test group). Cell suspensions were statically incubated in 5% CO2 at 37oC for additional 2 h. Then, cell suspensions were harvested by centrifugation and directly prepared to ultrastructural analysis by transmission electron microscopy (A=30000, Zeiss EM 900, Zeiss, Munich, Germany). One hundred cells of each microorganism were analyzed to evaluate the morphology of cellular wall and polysaccharidic capsule.
Results: Xylitol promoted alterations in morphology of Streptococcus mutans ATCC 33478 and Streptococcus sobrinus ATCC 25175, resulting in more diffuse and less defined cellular wall, more dispersive and irregular polysaccharidic capsules in comparison to control group.
Conclusion: The results demonstrated the ability of 20% xylitol in producing ultrastructural alterations in Streptococcus mutans ATCC 33478 and Streptococcus sobrinus ATCC 25175. Further in vitro studies are important to clarify the clinical action of xylitol in dental caries prevention.
Sponsors: FAPESP, CNPq, FGM/Brazil and DANISCO/Brazil.