The role of H2O2 and the lactoperoxidaseSCN−H2O2 system on the interaction between two bacteria originating from human dental plaque, Streptococcus rattus (mutans) BHT and Streptococcus mitior LPA-1, grown on human teeth in an artificial mouth (original) (raw)

1985, Archives of Oral Biology

Teeth were inoculated with either the organisms separately or with a freshly-prepared mixture of both. The apparatus was swept with 5 per cent (v/v) CO, in either air or N, , and incubated for 90 h. A nutrient supplement containing 1 per cent (w/v) glucose was supplied for 1 h in every 6 h. Both organisms achieved similar numbers when grown aerobically in pure culture, yet in mixed culture there was pronounced inhibition of BHT (p < 0.001). When the synthetic saliva was supplemented with catalase the strain BHT count in mixed culture was much higher (p < 0.001). It was concluded, therefore, that the strain LPA-I produced inhibitory levels of hydrogen peroxide (H,O,) on the tooth surface under aerobic conditions. This was supported by finding that a lower viable count of LPA-I in pure culture was attained when lactoperoxidase (LPO) was included in the saliva (p i 0.005), as all components of the LPGSCN-H,O, system were presumably present. With the Nr-CO, mixture, conditions were not strictly anaerobic and both catalase and LPO increased all viable counts. Under these conditions, therefore, when H,O, was limiting, LPO protected bacteria against its bactericidal effect.