Human Oral Microbiome and Systemic Diseases: What Stage are We at?

The oral cavity is a dynamic ecosystem comprising an array of microbial communities, including many pathogenic or opportunistic species. After the gut microbiome, the human oral microbiome is the largest microbial community in the human body [¹].

Recent studies have also demonstrated the role of periodontal disease as a risk factor or enhancer of distant systemic pathologies such as Alzheimer's disease and colorectal cancer with bacterial periodontopathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum, respectively [²,³].

Despite this, it is still not possible to affirm that the presence of certain species in regions other than the oral cavity is synonymous with a relationship with the disease, since many of the microorganisms present in the various regions of the mouth are also habitual residents in other regions such as the intestine [⁴] without this meaning that there was a migration from the oral cavity. Thus, for example, although there are studies showing a significant abundance of Porphyromonas gingivalis in patients with neurodegenerative diseases, they clarify that it is not known whether the microorganism is able to cross the blood-brain barrier [⁵] or is part of the resident microbial flora.

Since the publication of the results of the human microbiome project [⁶], it was shown that microorganisms do not have unique niches and their presence in various locations does not necessarily generate disease. We should emphasize that we are just beginning to know the characteristics of microbiomes, their variability influenced by various factors, and their interaction with the host. Therefore, it is responsible to indicate that more information is required with the deepening of the understanding of the association between the oral microbiome and other human microbiomes, since, in the future, they may be used as potential diagnostic biomarkers, screening tools and prognostic indicators, and interventions related to an altered human microbial composition may become the new adjuvant treatment in oral and systemic health.

References

• ¹
  Bourgeois D, Gonçalves LS, Lima-Junior JDC, Carrouel F. Editorial: The Oral Microbiome is a Key Factor in Oral and Systemic Health. Front Microbiol 2022; 13:855668. https://doi.org/10.3389/fmicb.2022.855668
  » https://doi.org/10.3389/fmicb.2022.855668
• ²
  Kapila YL. Oral health's inextricable connection to systemic health: Special populations bring to bear multimodal relationships and factors connecting periodontal disease to systemic diseases and conditions. Periodontol 2000 2021; 87(1):11-6. https://doi.org/10.1111/prd.12398
  » https://doi.org/10.1111/prd.12398
• ³
  Reitano E, de'Angelis N, Gavriilidis P, Gaiani F, Memeo R, Inchingolo R, et al. Oral bacterial microbiota in digestive cancer patients: a systematic review. Microorganisms 2021; 9(12):2585. https://doi.org/10.3390/microorganisms9122585
  » https://doi.org/10.3390/microorganisms9122585
• ⁴
  Gomaa EZ. Human gut microbiota/microbiome in health and diseases: a review. Antonie van Leeuwenhoek 2020; 113(12):2019-2040. https://doi.org/10.1007/s10482-020-01474-7
  » https://doi.org/10.1007/s10482-020-01474-7
• ⁵
  Dibello V, Lozupone M, Manfredini D, Dibello A, Zupo R, Sardone R, et al. Oral frailty and neurodegeneration in Alzheimer's disease. Neural Regen Res 2021; 16(11):2149-53. https://doi.org/10.4103/1673-5374.310672
  » https://doi.org/10.4103/1673-5374.310672
• ⁶
  Integrative HMP (iHMP) Research Network Consortium. The Integrative Human Microbiome Project. Nature 2019; 569(7758):641-8. https://doi.org/10.1038/s41586-019-1238-8
  » https://doi.org/10.1038/s41586-019-1238-8

Publication Dates

• Publication in this collection
  13 Mar 2023
• Date of issue
  2022

History

• Received
  12 Mar 2022
• Reviewed
  15 Mar 2022
• Accepted
  17 Mar 2022