Background and Aims
Incredibly diverse microbial communities (microbiota) are now routinely studied throughout the human body in the context of health and disease. In the mouth, microbiota play key roles in all oral diseases, including caries, periodontal disease, gingivitis, halitosis, and oral cancers. Of these, caries remains one of the most widespread and costly diseases in existence today – $8.7 billion AUD was spent to correct caries in 2012. These disease aetiologies are directly linked to the microbiota present in dental plaque biofilms. The microbiota contained within plaque biofilms are notoriously difficult to treat using physical removal or antibiotics. Elsewhere in the body, microbiota have been manipulated using transplantation (e.g. Faecal Microbiota Transplantation (FMTs)), where microbiota from one individual are placed into another, overriding the existing microbes. While FMTs are now common treatment for gut diseases (Clostrioides difficile infection), microbial transplants do not exist for the mouth, despite the promise they hold for treating recalcitrant oral diseases.
The aim of this study is to develop an in vitro oral microbiome transplant (OMT) as a new method to improve oral health.
Methodology
Plaque from three caries susceptible donors (SC) were grown in three separate 3D printed flow cells (FCs) containing hydroxyapatite discs for 10-days using artificial saliva media. After 10-days, biofilms on the discs were removed using 0.2% chlorohexidine and the FCs were then inoculated with plaque from healthy OMT donors and grown for 10-days. Plaque biofilm and planktonic cells were taken at each 10-day time-point for high-throughput DNA sequencing and metabolomics, respectively. Discs were also taken before and after chlorohexidine treatment for Scanning Electron Microscopy (SEM).
Results
SEM images of the SC microbiota showed that chlorohexidine removal of the microbiota was effective in all FCs. 16S rRNA analysis indicated that SC microbiota (PERMANOVA; pseduo-F=6.98; (q) = 0.027) were significantly different from donor microbiota 10-days post-transplantation, (PERMANOVA; pseduo-F=2.48; (q) = 0.063), suggesting that a new microbial community had established. The degree in oral microbiome transplantation varied between FCs. Metabolomics revealed significant differences between metabolites produced by SC and donor microbiota.
Conclusion
This study demonstrated the capability to grow a SC microbiota using an in vitro model over 10-days, followed by successful transplantation of a healthy donor microbiota. The significant differences in species detected and metabolites produced by SC and donor microbiota are unique findings in oral microbiome research. Additionally, this is the first ever successful oral microbiome transplant done in vitro.