Associations between Salivary Levels of Streptococcus mutans, Streptococcus sobrinus, Lactobacilli, and Caries Experience in Kenyan Adolescents

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Abstract
Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies-cultured from the saliva of each individual-to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 ± 6.43 and 1.46 ± 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8. 7 x 104 and 6. 7 x 104, respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p<0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p<0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.