Post-hydrogen Peroxide Effect in Peroxidogenic Oral Streptococci

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Abstract
The effects of inhibitory concentrations of hydrogen peroxide on the growth of 11 strains of four peroxidogenic species of oral streptococci (Streptococcus oralis, Streptococcus mitis. Streptococcus sanguis and Streptococcus sobrinus) were studied. The effect of H2O2 was measured as the post-hydrogen peroxide effect (PHPE), defined as the difference in the time necessary for the bacterial population in batch cult ure to increase by one decimal logarithmic unit of the number of colony forming units per millilitre, between cultures exposed to a concentration equal to the corresponding minimum inhibitory concentration of H2O2, and non-exposed cultures. No PHPE was shown by S. oralis NCTC 11427; other strains tested gave times ranging from 20 min (S. sanguis JENA 2697) to 9 h 15 min (S. mitis OGS 232). The PHPE appears to be strain- and species-dependent.