Introduction

The oral cavity is a complex and dynamic environment hosting a vast array of microorganisms that maintain a delicate balance to support host health. Among these is Aggregatibacter sp., a member of the Proteobacteria phylum. This organism plays a nuanced role within the oral ecosystem, acting as a commensal in some contexts while becoming associated with inflammatory processes in others. Understanding the functional potential of Aggregatibacter sp. is essential for recognizing how microbial diversity in the mouth reflects and influences systemic health.

Location of Microbe

Oral Ecosystem

Aggregatibacter sp. primarily colonizes the oral cavity, with a significant presence in subgingival biofilms. These biofilms are complex microbial communities that adhere to the tooth surface and periodontal pockets, where the bacteria interact with the host's gingival tissues.

Behavior During Dysbiosis

Oral Ecosystem

During states of oral dysbiosis, such as periodontitis, the microbial abundance of Aggregatibacter sp. can shift. In some inflammatory contexts, such as in patients with diabetes, these bacteria may be present at relatively lower levels compared to other potent pathogens like Tannerella forsythia, reflecting a shift in the ecological competition within the subgingival niche.

Disease Associations

Oral Ecosystem

Periodontitis

Aggregatibacter sp. is frequently associated with the subgingival microbiome of individuals suffering from periodontitis. Its presence within the periodontal pocket is often linked to a consortium of pathogens that contribute to the breakdown of the periodontal ligament and alveolar bone. The interaction between Aggregatibacter sp. and the host can trigger inflammatory signaling that exacerbates tissue damage.

Rheumatoid Arthritis (RA)

There is a documented association between Aggregatibacter species and the initiation of rheumatoid arthritis. Specifically, certain species like Aggregatibacter actinomycetemcomitans can trigger the overexpression of mammalian peptidyl arginine deiminase (PADI) from host neutrophils through the release of leukotoxin A. This process leads to the citrullination of proteins, which is a key step in the development of anti-citrullinated peptide antibodies (ACPA) that drive autoimmune responses in RA patients. Interestingly, in established RA, a reduction in Aggregatibacter sp. abundance has been associated with elevated ACPA levels, suggesting a complex host-microbe interaction where the immune system may eventually control the abundance of these bacteria.

Foods Supporting Healthy Balance

Maintaining a healthy oral ecosystem requires a diet that prevents the overgrowth of opportunistic pathogens while supporting a diverse microbial community. A diet rich in fibrous vegetables and fruits promotes the production of saliva and mechanical cleaning of the teeth, which helps regulate the biofilm composition and prevent the excessive accumulation of subgingival plaque. Reducing the intake of refined sugars is critical, as sugars provide the primary energy source for many acid-producing bacteria that can disrupt the oral pH and trigger dysbiosis, creating an environment where Aggregatibacter sp. and other periodontopathogens can thrive.

Additionally, incorporating foods rich in Omega-3 fatty acids (such as flaxseeds, walnuts, and fatty fish) may help modulate inflammatory signaling within the gums, supporting gut barrier integrity and the overall systemic inflammatory profile. Staying hydrated with water ensures adequate salivary flow, which contains essential antimicrobial proteins and minerals that keep the microbial abundance of the oral cavity in a homeostatic state.

Actionable Insights

• Prioritize Rigorous Oral Hygiene: Regular brushing and flossing are essential to disrupt subgingival biofilms, reducing the reservoir of opportunistic pathogens like Aggregatibacter sp.
• Manage Systemic Health: Since conditions like diabetes can shift the diversity of the subgingival microbiome, maintaining stable blood glucose levels may help prevent severe oral dysbiosis.
• Regular Dental Screenings: Professional cleanings can remove deep-seated plaque that cannot be reached by brushing, limiting the functional potential of periodontopathogens.
• Anti-Inflammatory Nutrition: Focus on a whole-food, plant-rich diet to reduce systemic inflammation, which may mitigate the trigger for autoimmune responses associated with oral citrullination.
• Monitor Gum Health: Be vigilant about bleeding gums or persistent bad breath, as these are early signs of a shift in microbial balance that requires professional intervention.

Conclusion

Aggregatibacter sp. is a significant component of the oral microbiome whose impact on health is highly dependent on the ecological context. While it exists as part of the normal flora, its association with periodontitis and its ability to trigger protein citrullination link it to systemic inflammatory conditions like rheumatoid arthritis. Maintaining a balance through oral hygiene and systemic health management is key to ensuring that this microbe remains a commensal rather than a driver of dysbiosis. By focusing on microbial diversity and the reduction of inflammatory triggers, individuals can better support their overall oral and systemic well-being.

A pilot study of red complex and three genera subgingival microbiome in periodontitis subjects with and without diabetes, evaluated by MinION platform

Anti-Citrullinated Peptide Antibodies Control Oral Porphyromonas and Aggregatibacter species in Patients with Rheumatoid Arthritis