the oral microbiome

see also:

• the GIT microbiome

• the oral microbiome is an overlooked cause of disease and the importance of dental health has a preventive medicine measure is inadequately funded
• it possesses the second-highest level of diversity after the gut microbiome, encompasses a wide array of bacterial genera and families
• in particular, chronic inflammatory states such as chronic gingivitis may drive IL-6 activity, hs-CRP and may potentially be an important driver of atherosclerosis and primary prevention - although this could also be due to Strept. viridans biofilms in blood vessels ¹⁾
• in 2025, a new form of giant circular DNA extrachromosomal elements (ECEs) named “Inocles” was discovered in oral microbiome, these massive strands of extrachromosomal DNA within oral bacteria average 350,000 base pairs – making them some of the largest extrachromosomal elements ever seen in the human microbiome. Inocles exhibit significant positive correlations with immune cells and proteins responding to microbial infection in peripheral blood. They seem to have marked reductions in patients of head and neck cancers and colorectal cancers.²⁾

• Strept. viridans as a very common oral commensal which may cause serious disease such as:
  • sub-acute endocarditis
  • may be the primary process contributing to coronary artery plaque rupture causing acute myocardial infarction (AMI/STEMI/NSTEMI) as it forms antibiotic and immune system resistant biofilms in endothelium which can remain dormant for years and become active in response to stress, viral infections, etc
  • see 2025: Viridans Streptococcal Biofilm Evades Immune Detection and Contributes to Inflammation and Rupture of Atherosclerotic Plaques
• they are generally resistant to most cephalosporins apart from 3rd gen ones such as ceftriaxone but more sensitive to penicillins such as amoxycillin
• they develop resistant genes rapidly to doxycycline (as do gut bacteria)

• Strept. mutans has a key role in creating dental caries and gingivitis

• the dominant factor in chronic gingivitis remains accumulation of microbial dental plaque due to poor oral hygiene
• this is thought to be due to diverse oral bacteria found in dental plaque, with several key species consistently implicated such as:
  • Streptococcus species (especially S. sanguinis, S. mitis, S. oralis, S. mutans) - these tend to be early colonizers of dental plaque
  • Actinomyces species (A. viscosus, A. naeslundii) promote chronic inflammation as part of mature biofilm
  • Fusobacterium nucleatum has a central in biofilm architecture and bridging between early and late colonizers
  • Veillonella species often present in mixed communities, contributing to overall plaque maturation
  • Treponema species (spirochetes) show increased abundance in more severe or chronic forms
• secondary or associated species:
  • Porphyromonas gingivalis more linked with periodontitis, can be present in chronic gingivitis, especially as inflammation advances
  • Streptococcus pneumoniae is not a common native dental plaque organism but can colonize dental plaque, especially in certain high-risk populations such as the elderly, hospitalized, or institutionalized patients and this may increase risk of community acquired pneumococcal pneumonia
  • Bacteroides/Prevotella species
  • Capnocytophaga, Eikenella, and Campylobacter - less commonly, but can be detected in gingivitis
  • fungi (eg. Candida albicans) and viruses may play a minor or modifying role but are not primary agents in chronic gingivitis

• oral bacteria can modulate the risk and severity of respiratory infections
• evidence supports a bidirectional association between the oral and lung microbiomes, suggesting implications for both the prevention and management of lung diseases
• numerous clinical studies have validated the efficacy of oral probiotics, such as Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus, in decreasing the occurrence of ventilator-associated pneumonia, acute upper respiratory tract infections, and COVID-19 infections
• certain periodontopathic bacteria like Fusobacterium nucleatum have been identified to induce IL-6 and IL-8 production, exacerbating conditions such as COPD
• Prevotella, Streptococcus, Fusobacterium, Pauljensenia, and Capnocytophaga play crucial roles in influencing respiratory infections ³⁾
  • Prevotella is associated with both promoting bronchitis and inhibiting pneumonia and tonsillitis, with a mixed effect on chronic sinusitis
  • Streptococcus and Fusobacterium show varied impacts on respiratory diseases
  • Fusobacterium promoting chronic sinusitis, bronchiectasis, and bronchitis
  • Pauljensenia and Capnocytophaga are linked to reduced bronchitis and tonsillitis, and inhibited pneumonia and bronchitis, respectively
  • Streptococcus pneumoniae is not a common native dental plaque organism but can colonize dental plaque, especially in certain high-risk populations such as the elderly, hospitalized, or institutionalized patients and this may increase risk of community acquired pneumococcal pneumonia

• the oral microbiome appears to have critical role, where dysbiosis significantly contributes to the pathogenesis of tonsillar diseases
• Neisseria lactamica, traditionally viewed as a commensal organism, is now linked to an elevated risk of tonsillitis due to its potential to modulate immune responses in the mucosa, suggesting its role in increasing susceptibility to this condition
• Campylobacter rectus, often associated with periodontal disease, has been found in the tonsillar crypts of both affected and unaffected individuals, with this study confirming its consistent association with a heightened risk of tonsillitis
• Porphyromonas endodontalis, known for its presence in periodontal infections, has been detected in those with recurrent tonsillitis, underscoring the interconnectedness between oral health and tonsillar pathology
• Streptococcus sanguinis, a normal component of the oral microbiota, has been identified as a protective factor against recurrent streptococcal tonsillitis, likely through competitive inhibition or immune modulation

• chronic sinusitis is associated with measurable alterations in the oral microbiome, often involving increased prevalence of periodontal pathogens and shifts in bacterial populations linked to both oral and sinus inflammation
• studies show a higher abundance of Fusobacterium, Prevotella, Porphyromonas, Veillonella, Streptococcus mitis, and Rothia mucilaginosa in people with chronic sinusitis, especially those with concurrent dental disease or poor oral hygiene
• oral dysbiosis — such as overgrowth of periodontopathogenic bacteria — can directly impact sinus health, with odontogenic (dental origin) disease accounting for up to 40% of chronic sinusitis cases in some series
• chronic inflammation, bone erosion, or abscesses in the upper teeth enable oral bacteria to migrate into the maxillary sinuses, further altering both oral and sinus microbiota communities