LONGITUDINAL SURVEY OF THE DISTRIBUTION OF VARIOUS SEROTYPES OF STREPTOCOCCUS-MUTANS IN INFANTS

The establishment of various serotypes of S. mutans was studied serologically in plaque samples collected from labial surfaces of upper primary incisors of 22 infants (starting age, 5-13 mo.) for 30 mo. Clinical examinations were also performed. No clear-cut association between the initiation of dental caries and previous detection of S. mutans was noted. All 12 of the infants with caries had S. mutans isolated at some time during this study. The most common serotype isolated at the initial establishment of S. mutans on the tooth surfaces was serotype c; types d, e and g became established in a few cases. During the test period, changes in the distribution of serotypes of S. mutans were observed in some cases. The initiation of carious lesions could be found in a few cases even when S. mutans comprised about 1% or less of the total streptococcal count of the specimen from the tooth surfaces. Serotype d/g strains tended to develop carious lesions on smooth surfaces, although serotype c was isolated from almost all individuals who developed caries.