The oral microbiome is a complex ecosystem, hosting a wide range of microbial species that interact dynamically with each other and their host. This balance, or homeostasis, is vital for maintaining oral and systemic health. However, dysbiosis—or microbial imbalance—can lead to significant health issues. Locally, it can manifest as dental caries, periodontitis, or oral candidiasis, while its systemic implications range from gastrointestinal disorders and cardiovascular diseases to neurological conditions, diabetes, autoimmune diseases, and adverse pregnancy outcomes. These systemic effects underscore the oral microbiome’s profound connection to various organ systems.
Oral microbes, under specific conditions, can transition from benign to pathogenic, exacerbating disease progression. For instance, periodontal diseases are associated with the proliferation of Gram-negative bacteria like P. gingivalis, which can worsen cardiovascular disease (CVD) by promoting systemic inflammation and platelet aggregation. Similarly, oral pathogens have been implicated in metabolic and neurological disorders. P. gingivalis has been detected in the brains of Alzheimer’s disease patients, where it provokes neuroinflammation. Furthermore, its virulence factors, such as gingipain R1, have been linked to Parkinson’s Disease and hypercoagulable states, highlighting the bacterium's role in systemic disease mechanisms.
The interconnectedness of the oral microbiome with other systems is further evident in its relationship with the gut microbiome. The oral–gut axis allows for the translocation of oral bacteria to the gastrointestinal tract, particularly under pathological conditions like inflammatory bowel disease (IBD) or colon cancer. This microbial migration can disrupt gut homeostasis, influencing metabolic health and systemic inflammation. Alterations in oral microbial populations, driven by factors such as diet, hygiene, smoking, or systemic illnesses, play a pivotal role in these processes, demonstrating how lifestyle and health status can shape systemic disease risks through the oral microbiome.
Moreover, specific oral bacteria contribute to autoimmune diseases. For example, P. gingivalis produces a virulence factor, bacterial protein arginine deiminase (PPAD), which can citrullinate host proteins, triggering an autoimmune response. This mechanism is particularly significant in conditions like Rheumatoid Arthritis, where anticitrullinated protein antibodies (ACPAs) are a hallmark. Such findings reinforce the oral microbiome's critical role in initiating and perpetuating systemic inflammatory and autoimmune pathways, positioning oral health as a central pillar of overall health.
Rajasekaran, J. J., Krishnamurthy, H. K., Bosco, J., Jayaraman, V., Krishna, K., Wang, T., & Bei, K. (2024). Oral Microbiome: A Review of Its Impact on Oral and Systemic Health. Microorganisms, 12(9), 1797. https://doi.org/10.3390/microorganisms12091797
Santacroce, L., Passarelli, P. C., Azzolino, D., Bottalico, L., Charitos, I. A., Cazzolla, A. P., Colella, M., Topi, S., Godoy, F. G., & D'Addona, A. (2023). Oral microbiota in human health and disease: A perspective. Experimental biology and medicine (Maywood, N.J.), 248(15), 1288–1301. https://doi.org/10.1177/15353702231187645’