Xylitol is effective in preventing acute
otitis media by inhibiting the growth of Streptococcus pneumoniae. To clarify this inhibition we used
fructose, which is known to block similar growth inhibition observed in Streptococcus mutans. In addition, we evaluated the efficacy of
sorbitol in inhibiting the growth of pneumococci, as
sorbitol is widely used for indications similar to those for which
xylitol is used. The addition of 5%
xylitol to the growth medium resulted in marked growth inhibition, an effect which was totally eliminated in the presence of 1, 2.5, or 5%
fructose but not in the presence of 1 or 5%
glucose, 1%
galactose, or 1%
sucrose. This finding implies that
xylitol-induced inhibition of pneumococcal growth is mediated via the
fructose phosphotransferase system in a way similar to that in which mutans group streptococcal growth is inhibited. The addition of
sorbitol at concentrations of 1, 2.5, or 5% to the growth medium did not affect the growth of pneumococci and neither inhibited nor enhanced the
xylitol-induced growth impairment. Thus, it seems that
xylitol is the only commercially used
sugar substitute proven to have an antimicrobial effect on pneumococci.