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

Abstract

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