Determining the spatial distribution of viable and nonviable bacteria in hydrated microcosm dental plaques by viability profiling

Abstract

Aims. The aim of this study was to use confocal laser scanning microscopy (CLSM) to examine the spatial distribution of both viable and non-viable bacteria within microcosm dental plaques grown in vitro. Previous in vivo studies have reported upon the distribution of viable bacteria only. Methods and Results. Oral biofilms were grown on hydroxyapatite (HA) discs in a constant-depth film fermenter (CDFF) from a saliva inoculum. The biofilms were stained with the BacLightTM LIVE/DEAD system and examined by CLSM. Fluorescence intensity profiles through the depth of the biofilm showed an offset between the maximum viable intensity and the maximum non-viable intensity. Topographical differences between the surface properties of the viable and non-viable biofilm virtual surfaces were also measured Conclusions. The profile of fluorescence intensity from viable and non-viable staining suggested that the upper layers of the biofilm contain proportionally more viable bacteria than the lower regions of the biofilm. Significance and Impact of Study. Viability profiling records the transition from predominantly viable to non-viable bacteria through biofilms suggesting that this technique may be of use for quantifying the effects of antimicrobial compounds upon biofilms. The distribution of viable bacteria was similar to that found in dental plaque in vivo suggesting that the CDFF produces in vitro biofilms which are comparable to their in vivo counterparts in terms of the spatial distribution of viable bacteria.