Objective To preliminarily investigate the relationship between the Lactate dehydrogenase (LDH) activity ofStrep- tococcus mutans(S.mutans)and dental caries initiation.Methods 100S. mutansstrains derived from caries-active and caries- free individuals were cultured in BHI medium supplemented with glucose. Cells were extracted and ruptured, and the extracted liquid proteinwas quantifiedwith Coomassie brilliant blue G250 stainingmethods. LDHactivitywas assayed usingthe pyruvate-de- pendent oxidation of NADH-with and without FDP.Results LDH activity of the two groups strains had no difference (P> 0·05), but the distribution of differ class enzyme activity strains in the two groups was different (P
