P33 In vitro perfusion biofilm model for the growth of oral microbes associated with oral malodour

Abstract

Objectives Oral malodour is mainly due to the generation of volatile sulphur compounds (VSC) by oral anaerobes present in the tongue biofilm. The aim of this study was to evaluate the use of a biofilm system to model the ecology and VSC physiology of tongue biofilm microcosms. Of particular interest was the use of the model to maintain a high diversity of bacterial groups and study their response to environmental changes including exposure to VSC substrates and inhibitors.Methods Biofilms were grown using a Sorbarod perfusion model modified by supply of anaerobic gas to grow oral anaerobes. Sorbarods were inoculated using tongue scrape suspension containing 3 × 108 cfu ml−1 and pre‐incubated anaerobically for 24 h at 37°C to promote cell adhesion. After 24 h, the biofilm system was perfused at 12 ml h−1 with BHI (0.74 g L−1) supplemented with haemin, cysteine and/or DTT. Biofilms and eluates (released cells) were sampled up to 96 h and numbers of broad bacterial groups enumerated by selective media. VSC production was measured using a HalimeterTM.Results Repeated analysis of biofilms showed that a quasi‐steady state was achieved between 48 and 96 h. The mean specific growth rate was 0.018 h−1. Ecological analysis showed all broad groups were maintained at a constant proportion reflecting the original inoculum for both biofilms and eluates. VSC specific activity was upregulated when biofilms were perfused with appropriate VSC‐substrates (cysteine, glutathione and methionine). In situ exposure of the biofilms to pulses of putative inhibitors (Zn, H2O2 and chlorhexidine) at a range of concentrations typically used in vivo gave dose‐dependent inhibition of VSC production (for Zn and H2O2) and reduced viable numbers by one to two log‐fold (H2O2 and chlorhexidine).Conclusions The modified Sorbarod perfusion model is suitable for maintaining high diversity biofilms representative of the tongue flora in terms of both ecological behaviour and response towards VSC substrates and inhibitors.