Isolation and serotyping of Streptococcus mutans from teeth and feces of children

Streptococcus mutans were detected in the feces from 10 of 29 caries-active patients, aged 4 to 9 years. The percentage of S. mutans to the total counts of facultatively anaerobic streptococci on mitis salivarius agar (Difco Laboratories) varied from 0 to 72.5%. S. mutans were then isolated from dental plaque of sound teeth and carious dentin of the 10 subjects known to harbor S. mutans in the feces. The frequency distribution of various serotypes of these dental and fecal isolates of S. mutans was compared by the immunodiffusion technique. Of the total 1,047 isolates (290 isolates from feces, 289 from dental plaque, and 468 from carious dentin), type c isolates were most prevalent (ca. 66%). Serotype d, e, f, and g isolates were also found but in far lower frequencies. Plural serotypes of S. mutans were occasionally found in dental and fecal samples of a single subject. For two subjects, relatively rare serotypes of S. mutans in the population examined, serotype e, f, or g, were predominantly found in their fecal and dental samples and those of their siblings and mother, suggesting an intrafamilial transmission of S. mutans.