Distribution and Isolation Frequency of Eight Streptococcal Species in Saliva from Predentate and Dentate Children and Adults

Abstract

The isolation frequency and distribution of eight recently defined streptococcal species have been investigated in the saliva of adults and that of both predentate and dentate children. The effects of frequency of sugar intake and tooth presence on the distribution of streptococcal species were also analyzed. Saliva samples were collected from 121 subjects divided into three study groups: (a) 56 predentate children (predentate group), (b) 37 dentate children (dentate group), and (c) 28 adults (adult group). Up to 17 biochemical and enzymatic tests were used to categorize streptococcal isolates into S. mitis, S. oralis, S. salivarius, S. anginosus, S. sanguis, S. vestibularis, S. mutans, and S. gordonii.The mean total and streptococcal salivary colony-forming units (CFU) were lowest in the predentate group and highest in the adult group. Streptococci were found in all the study subjects, and there was no obvious relationship between the total or streptococcal CFU and the number of teeth or the frequency of sugar intake. There was a wide variation in the isolation frequency of streptococcal species in the three study groups. S. mitis, S. oralis, and S. salivarius were the most frequent species isolated, and together they comprised 83% of the total streptococcal isolates. In contrast to studies using older classifications, S. sanguis was a minor species in the saliva though found more often in adults than in children (p < 0.04). S. anginosus was a minor species found in about 10% of adults and children. S. gordonii was detected rarely and only in dentate subjects. S. mutans was detected only in dentate subjects, significantly greater in adults (57.1%) than in children (5.4%, p < 0.001). In contrast, S. vestibularis was found in both dentate and predentate children but not in adults. No relationship between the isolation frequency of any of the species and sugar intake in children was demonstrated. The new classification of streptococci has revealed major differences in isolation frequency and distribution of the individual species and should prove useful in future studies of ecological factors affecting oral flora.