Biological Model for the Identification of Malodour Control Agents

Objective: To develop and characterise a tongue-derived microcosm biofilm to evaluate potential anti-malodour actives with antimicrobial and/or VSC-neutralising activity.

Methodology: Inoculum was generated from 1 subject using a sterile toothbrush firmly brushed against the posterior dorsum of the tongue. Sterile sorbarod filters (n=3) were inoculated and incubated anaerobically for 24hours to allow bacterial attachment. Filters were then attached to the system and biofilms cultivated for a further 24 hours with continuous perfusion of sterile lab air (50 mL/hour) and media (36 mL/hour). Media comprised 1/5th strength BHI supplemented with dithiothreitol, L-cysteine and haemin. Chlorhexidine digluconate (0.2%v/v), copper gluconate (0.1%w/v) and zinc acetate (0.1%w/v) were evaluated. Baseline gas samples were collected. Subsequently, biofilms were exposed to test agents for 1 min (static conditions). Flow was then resumed, and samples collected at intervals upto 60min. Biofilm gas samples were analysed for VSC using gas chromatography with flame photometric detection.

Results: Both metal solutions significantly reduced biofilm-generated total VSC levels. Copper gluconate reduced both methyl mercaptan and hydrogen sulfide levels to zero over the first 10min, at which point total VSC levels gradually increased to reach approximately 90% of baseline after 60min. In contrast, zinc acetate had a major impact only on hydrogen sulphide levels, and methyl mercaptan levels were unaffected. Exposure of biofilms to chlorhexidine digluconate resulted in an initial increase in VSC levels which returned to baseline within 10 minutes.

Conclusion: The developed methodology has shown that metal ions are able to significantly reduce the levels of VSC generated from a tongue-derived microcosm biofilm. Further, the model was able to discriminate between the activity of a traditional antimicrobial and two VSC neutralisation agents.