The role of saliva in the persistence ofStreptococcus gordoniiin water

Abstract

Introduction: Streptococcus gordonii is one of the pioneer colonizer of the oral cavity and may be isolated from dental unit waterlines (DUWL) mixed with saliva because of antiretraction valve dysfunction.Aims: The behavior of S. gordonii in tap-water and the influence of low saliva concentrations (0–10% v/v) on bacterial proliferation were investigated. We evaluated the effect of saliva on bacterial survival in tap-water in order to know if it could facilitate or not the biofilm formation in the context of DUWL.Materials and methods: S. gordonii’s (DL1) survival ability was evaluated in tap-water with or without saliva supplementation (0–10% v/v) at 20 °C and 27 °C. Whole unstimulated saliva (WUS) and artificial saliva (AS) were both tested in this study. A gas chromatography and mass spectrometry (GC/MS) analysis was performed on filtered lyophilized WUS and the effect of each AS’s components were evaluated on S. gordonii’s survival.Results: S. gordonii survived in tap-water no longer than: 24 h at 27 °C and 72 h at 20 °C; water supplementation with saliva induced the bacterial inoculum maintained at 20 °C (>1% v/v) and enabled bacteria to survive up to 7 days at 27 °C (≥5% v/v). Various most simples structural artificial saliva’s compounds (both proteic and carbohydrate) seemed participate to this survival improvement.Discussion: Even if saliva contains some antimicrobial agents like lysozyme, it can also have a positive effect on S. gordonii. Very few information are known on saliva’s compounds responsible of this effect.Conclusion: Saliva, even in low proportions (1–10% v/v), was able to facilitate the survival of S. gordonii in tap-water. Several of its components seem participate on this effect.