Treponema denticola

Treponema denticola is a Gram-negative anaerobic spirochete bacterium that is commonly found in the human oral cavity. It is one of the main pathogens associated with periodontal disease, a chronic inflammatory condition affecting the tissues surrounding the teeth.

Morphology

Treponema denticola is characterized by its unique helical shape, typical of spirochetes. It is a slender, tightly coiled bacterium, approximately 0.2 to 0.5 micrometers in diameter and 6 to 15 micrometers in length. The bacterium is motile, possessing endoflagella that run along the length of the cell, allowing it to move in a corkscrew motion.

Genomic Characteristics

The genome of Treponema denticola has been fully sequenced, revealing a circular chromosome of approximately 2.8 million base pairs. The genome encodes for a variety of proteins involved in metabolism, virulence, and motility. Notably, T. denticola possesses genes for proteolytic enzymes that degrade host tissues and immune evasion mechanisms.

Pathogenicity

Treponema denticola is a key component of the red complex, a group of bacteria strongly associated with periodontitis. It contributes to disease through several mechanisms:

• Adhesion: T. denticola adheres to host cells and extracellular matrix components using adhesins.
• Invasion: The bacterium can invade gingival epithelial cells, disrupting cell junctions and penetrating deeper tissues.
• Tissue Destruction: It produces proteases such as dentilisin, which degrade collagen and other structural proteins.
• Immune Modulation: T. denticola can modulate the host immune response, evading detection and promoting chronic inflammation.

Clinical Significance

Treponema denticola is implicated in the progression of periodontal disease, which can lead to tooth loss and has been associated with systemic conditions such as cardiovascular disease and diabetes mellitus. Detection of T. denticola in subgingival plaque is often used as a diagnostic marker for periodontal disease.

Diagnosis

Diagnosis of Treponema denticola infection is typically performed using:

• Polymerase Chain Reaction (PCR): Highly sensitive and specific for detecting T. denticola DNA in clinical samples.
• Microscopy: Dark-field or phase-contrast microscopy can visualize the spirochete's characteristic morphology.
• Culture: Although challenging due to its fastidious nature, T. denticola can be cultured under anaerobic conditions.

Treatment

Management of infections involving Treponema denticola includes:

• Antibiotics: Metronidazole and doxycycline are commonly used to target anaerobic bacteria.
• Mechanical Debridement: Scaling and root planing to remove subgingival plaque and calculus.
• Antimicrobial Mouth Rinses: Chlorhexidine gluconate can reduce bacterial load.

Research Directions

Ongoing research is focused on understanding the molecular mechanisms of Treponema denticola pathogenicity and its interactions with other oral microbiota. Novel therapeutic approaches, including vaccines and probiotics, are being explored to prevent and treat periodontal disease.

See Also

• Periodontal disease
• Spirochaetes
• Oral microbiome

External Links

• NCBI Genome Database: Treponema denticola
• CDC Oral Health