A simple method for determining extracellular polysaccharide-producing ability of oral streptococci.

A simple method is described for determining the types of extracellular polysaccharides produced by oral streptococci. The method yields quantitative results in which the amount of polysaccharides produced is normalised with respect to DNA. Results correlate well with previously published data for oral streptococci, except in the case of Streptococcus oralis for which there is no previously published data. All species within the mutans group produced both soluble and insoluble glucan; while soluble fructan was only produced by strains of Streptococcus rattus and Streptococcus mutans. The major extracellular polysaccharide produced by Streptococcus salivarius was soluble fructan, although some strains produced soluble and insoluble glucan. Most Streptococcus sanguis strains produced soluble and insoluble glucan. Soluble fructan was produced by some strains of S. sanguis and S. oralis. The latter also produced soluble and insoluble glucan. No detectable extracellular polysaccharide was elaborated by Streptococcus milleri, Streptococcus faecalis or Streptococcus lactis.