Distribution and Evaluation of Streptococcus sobrinus in Saliva Samples

Abstract

Streptococcus mutans（S. mutans）and Streptococcus sobrinus（S. sobrinus）can be isolated from the human oral cavity. S. sobrinus varies in many aspects, including serotype, hemolytic nature, and glucan aggregation ability, distinguishing its properties and functions from those of S. mutans. In addition, S. sobrinus exhibits significant cariogenicity correlating with smooth-surface caries. Though identifying the behavior of S. sobrinus and its correlation with caries is essential, little research has been conducted to assess the utility of the distribution and reference levels of S. sobrinus in caries activity tests and risk diagnoses. The prevention of transmission of cariogenic bacteria is incorporated in food and nutrition education and support in maternal and child health. To further manage and prevent such transmission, health workers of interprofessional collaboration should also include infants in their healthcare plan, determine the number of S. mutans and S. sobrinus in the saliva of adults in their 20s to 30s, and manage the cariogenic risks. Hence, this study aimed to investigate and comparatively assess the number of S. sobrinus and the ratio of S. sobrinus to total Streptococci（Ss/Ts）using the saliva of adults in their 20s. The accumulated primary data will be used to develop a simple culture assay for caries risk assessment. Results revealed that when classifying risks into two levels according to the number of S. sobrinus, either of the following two categories is appropriate: ≥1.0 × 10 5 as high risk and ≤1.0 × 10 5 as low risk. The Ss/ Ts is also appropriate to classify the risk levels in either of the two categories as fol-lows: ≥0.1 % as high risk and ≤0.1 % as low risk. In conclusion, the results of the present study suggest that cell cultures can be used to compare and estimate the number of S. sobrinus and the Ss/TS ratio in saliva for caries risk