Selection of a Micromethod and Its Use in the Estimation of Salivary Streptococcus mutans and Lactobacillus Counts in Relation to Dental Caries in Tanzanian Children

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Abstract
Three micromethods for the estimation of Streptococcus mutans and lactobacilli were compared. A micropipette method was selected because of its ability to detect low levels of the organisms and its high agreement with the conventional plating method and efficient use of agar medium. The trypticase yeast cystine sucrose bacitracin agar was found to be superior to the mitis salivarius bacitracin agar. Stimulated saliva of 144 Tanzanian children from the rural and urban areas in Morogoro was investigated for S. mutans and Lactobacillus counts. Both organisms were observed in all Tanzanian children. The mean S. mutans and Lactobacillus counts were 5.0 ± 0.9 and 4.5 ± 0.9 log cfu/ml saliva, respectively. S. mutans counts greater than 106 cfu/ml saliva were observed in 25% of the urban children and in 5% of the rural children. The caries prevalence was rather low and weakly correlated with the S. mutans and Lactobacillus counts. The Tanzanian children with a high S. mutans count but with a low caries experience were considered as caries-inactive at present, but at risk of developing dental caries by changing dietary habits.