OBJECTIVETo compare the production of organic acid of different genotype Streptococcus mutans (S. mutans) isolated from children with different caries experience.

METHODS66 strains of S.mutans isolated from dental plaques of children aged from 3 to 5 with different caries experience were chosen as test bacteria. The quantities of organic acid include formic acid, acetic acid and lactic acid which produced by different genotype of S. mutans, were measured by gas chromatograph.

RESULTSThere were significant difference in production of organic acid among the different genotypes of S. mutans isolated from children with different caries susceptibility, and so were the strains isolated from children within the same caries susceptibility (P < 0.05). The more genotypes the strain had, the more organic acid it produced (P < 0.05). Among all the organic acid, the quantity of lactic acid was much more than that of formic acid and acetic acid.

CONCLUSIONSThere were significant difference in the ability of the strains with different genotypes to produce organic acid, and the more genotypes it has, the more organic acid it produced.