A New Selective Medium for Streptococcus mutans and the Distribution of S. mutans and S. sobrinus and Their Serotypes in Dental Plaque

Abstract

A new selective medium (MS-MUT) was developed for the isolation of Streptococcus mutans from clinical specimens. The average growth recovery of S. mutans on MS-MUT medium was 72.4% of that on MS medium. Growth of Streptococcus sobrinus was significantly inhibited on the medium with an average recovery of 0.034%. In 103 subjects, S. mutans was detected at 58.3, 75.0 and 95.7% in the dental plaque of caries-free (CF), caries-inactive (CI) and caries-active (CA) subjects, respectively. S. sobrinus was detected in 8.3, 13.6 and 38.3% of CF, CI and CA subjects, respectively. S. sobrinus alone was detected in only 4.3% of CA subjects. The subjects in whom neither S. mutans nor S. sobrinus were detected were 41.6% in CF and 25.0% in CI. The most predominant serotype was c with a 67% detection rate. S. sobrinus, serotypes d or g were usually found together with S. mutans.