Growth inhibition of Streptococcus mutans by cellular extracts of human intestinal lactic acid bacteria

The in vitro growth of Streptococcus mutans was completely inhibited by water-soluble extracts from cells of various intestinal lactic acid bacteria identified as Streptococcus faecium, Streptococcus equinus, Lactobacillus fermentum, and Lactobacillus salivarius. The growth inhibition was dependent on the concentrations of the extracts. In contrast, the extracts did not inhibit the growth of the major indigenous intestinal lactic acid bacteria isolated from humans. These lactic acid bacteria were not acutely toxic in mice.