The tissues around the tooth, which include the gum and the bone supporting the tooth, comprise the periodontal tissues. Any infection of these tissues, initiated by oral disease-causing microorganisms that colonize the biofilms on the tooth surface, leads to this infection, known as periodontitis. As a result, the host immune response plays a major role in causing and spreading periodontal disease.
It's fascinating how humans have evolved alongside trillions of microorganisms distributed throughout the body. These specific ecosystems at each site perform unique functions and coexist harmoniously to support normal physiological processes. However, when these ecosystems (microbiota) are disturbed, they can have dangerous and even fatal effects, impacting both local and distant sites within the body. In the context of oral infections, inflammation of the periodontal tissue (tissues surrounding the tooth, such as gums and bone) and subsequent infections can extend beyond the tooth, migrating to the gastrointestinal tract. Understanding this complex interplay of microorganisms and how they cause disease can provide insights into therapeutic opportunities.
Similar to the oral microbiota, the unique environment in the gut constitutes a complex ecosystem, forming the largest community of microorganisms in the body. It plays a crucial role in maintaining physiological homeostasis, including immune system regulation and education. Additionally, it aids in digestion and acts as a barrier against exogenous pathogens, thereby preserving normal homeostasis. Disruption of the gut ecosystem can lead to gut dysbiosis (an imbalance of microbial species), resulting in conditions such as irritable bowel syndrome, inflammatory bowel disease, and colorectal cancer. Numerous studies, using sequencing techniques, have identified oral microorganisms within the lumen or mucosal cells of the gut. Some of these organisms, such as P. gingivalis and F. nucleatum, have been detected in the gut microbiota, suggesting ectopic colonization by oral microorganisms.
The first is hematogenous spread, which entails circulation through the blood. In the event of mechanical injury in the oral cavity, microorganisms can enter the bloodstream and reach the gastrointestinal tract. This has also been confirmed through blood analysis, revealing causative organisms in patients with oral health diseases such as periodontal disease. Additionally, certain Fusobacterium strains have been implicated in tumor colonization, suggesting spread through the circulatory system. Immune cells such as dendritic cells and macrophages are also hijacked, further facilitating the spread of organisms to the gastrointestinal tract.
The second route is enteral dissemination (within the digestive system). Humans swallow their saliva around 600 times a day, ingesting approximately 1.5 liters of saliva daily. Sharing of many microorganisms between the oral and gut microbiota, even in healthy individuals, is normal. Generally, oral microbes are poor colonizers in the gut due to multiple barriers, including the acidic environment. However, in conditions such as gastric achlorhydria (a condition where normal production of gastric acid is decreased or absent) and gastrointestinal diseases such as IBD (Irritable bowel disease) and GERD (Gastroesophageal reflux disease), where patients are treated with proton pump inhibitors, the path for oral microbes becomes easier. Among all oral microbes, P. gingivalis can survive the acidic barrier quite well. Another barrier to oral microbes in the gut is the harmonious structure present in gut microbes. However, in cases where patients are treated with antibiotics like vancomycin, oral microbes can expand and flourish in the gut.
To sum it up, it's crucial to further study the connection between oral and gut microorganisms. The detection of oral microorganisms is vital for risk assessment in patients with digestive system diseases. Alongside this assessment, companion diagnostics, which are other diagnostic tools, can be used to evaluate disease flare-ups. This can aid in the prevention and avoidance of digestive system diseases. Additionally, evaluating oral microorganisms and oral health can assist in developing drugs that target the colonization of oral microorganisms in the gut. These drugs can also inhibit inflammation and inflammatory byproducts caused by oral microbial colonization in the gut.
1. Kitamoto S, Kamada N. Periodontal connection with intestinal inflammation: Microbiological and immunological mechanisms. Periodontol 2000. 2022 Jun;89(1):142-153. doi: 10.1111/prd.12424. Epub 2022 Mar 4. PMID: 35244953; PMCID: PMC9018512.
(Input from various sources)
(Rehash/Dr. Manav Chaturvedi/SB)