The effect of inoculum source and fluid shear force on the development of in vitro oral multispecies biofilms

Aims: Saliva has been previously used as an inoculum for invitro oral biofilm studies. However, the microbial community profile of saliva is markedly different from hard- and soft-tissue-associated oral biofilms. Here, we investigated the changes in the biofilm architecture and microbial diversity of invitro oral biofilms developed from saliva, tongue or plaque-derived inocula under different salivary shear forces. Methods and Results: Four inoculum types (saliva, bacteria harvested from the tongue, toothbrush and curette-harvested plaque) were collected and pooled. Biofilms (n >= 15) were grown for 20 h in cell-free human saliva flowing at three different shear forces. Stained biofilms were imaged using a confocal laser scanning microscope. Biomass, thickness and roughness were determined by image analysis and bacterial community composition analysed using Ion Torrent. All developed biofilms showed a significant reduction in observed diversity compared with their respective original inoculum. Shear force altered biofilm architecture of saliva and curette-collected plaque and community composition of saliva, tongue and curette-harvested plaque. Conclusions: Different intraoral inocula served as precursors of invitro oral polymicrobial biofilms which can be influenced by shear. Significance and Impact of the Study: Inoculum selection and shear force are key factors to consider when developing multispecies biofilms within invitro models.