Peroxide and peroxidogenic bacteria in human saliva

Among the metabolites held responsible for the equilibrium among microbial species found in human saliva, hydrogen peroxide has occupied a prominent position. McLeod and Gordon (1922) first reported on bacterial production of peroxide and studied the inhibition of heterolo-gous organisms by the peroxide formed by pneu-mococcus. Thompson and Johnson (1951) con-cluded "that the inhibitory properties of most salivas are due to the hydrogen peroxide pro-duced by the mitis type streptococci." While the bacterial production of peroxide in vitro has been well established, only two studies deal with its occurrence in vivo. Wurster (1886, 1889) claimed to have detected hydrogen peroxide in every saliva. WVe may discount his claim for his reagent, tetramethylparaphenylendiamine, demonstrates indophenol oxidase rather than hydrogen peroxide (Berger, 1953). More recently Tschesche et al. (1951) reported that they detec-ted hydrogen peroxide in saliva. They estimated the concentration as 0.03 per cent (300,ug/ml). If saliva were to contain such a bactericidal con-centration (Berger, 1953) of hydrogen peroxide, one should expect that other investigators could substantiate the finding. To contribute to the understanding of the in vivo significance of peroxide in saliva the following types of experiments were undertaken: The determination of hydrogen peroxide in saliva, the estimation of the number of peroxidogenic bacteria, and the study of peroxide decomposition in saliva. a MATERIALS AND METHODS Peroxide determination. Tschesche et al. (1951) claimed that titanium sulfate did not react with saliva directly but gave the yellow color reactio