Objective To investigate the initial colonization ofMutans streptococci (MS) on teeth of children.Methods Dental plaque was collected from 123 children aged from 7 to 42 months.MSwas isolated by culturing on selective medium and i- dentified by biochemical tests.Results MSwas detected in 51 of 123 children. The rate of colonization was 41·5%, and the mean age of colonizationwas 29 month. The incidence ofMSinfection increasedwith age and tooth eruption, and reached peak at 25~31 months, whichwas statistically significant. There was a correlation between infection ofMSand dental caries.Conclusion The results indicate that the susceptive period ofMSinfection is from 25 to 31 months when the second primary molars erupt. MSinfection is associated with dental caries.
