Prevotella spp.: Anaerobic Oral Pathogens and qPCR Detection

The genus Prevotella belongs to the phylum Bacteroidetes and was reclassified from former Bacteroides species. These bacteria are non-spore-forming, non-motile, and exhibit pleomorphic shapes ranging from short rods to coccobacilli.

They are prominent members of the oral anaerobic microbiota, accounting for approximately 20–30% of total anaerobic bacteria in the oral cavity.

Prevotella spp. are strictly anaerobic and highly sensitive to oxygen. They are chemoorganotrophic, fermenting carbohydrates to produce metabolic end products such as acetate and succinate.

In laboratory settings, they are cultured on blood agar supplemented with vitamin K₁ and hemin under anaerobic conditions at 37°C. Colonies typically appear within 48–72 hours, measuring 1–3 mm in diameter.

Some species produce black pigment upon prolonged incubation (5–7 days), resulting from oxidation of heme-derived compounds.

Although part of normal flora, Prevotella spp. can become pathogenic under conditions such as immune suppression or tissue damage. Their pathogenicity is associated with several virulence factors:

• Lipopolysaccharide (LPS): Induces inflammatory responses
• Proteolytic enzymes: Including proteases and collagenases that degrade host tissues
• Pigment production: May enhance resistance to oxidative stress

These factors enable tissue invasion and contribute to mixed anaerobic infections.

Prevotella spp. are commonly involved in polymicrobial infections affecting multiple body systems:

Oral and maxillofacial infections: Periodontitis, dental abscesses, and post-extraction infections, often with foul-smelling pus.

Genital tract infections: Associated with bacterial vaginosis and pelvic inflammatory disease, often in synergy with Gardnerella vaginalis.

Respiratory infections: Aspiration of oral flora can lead to lung abscesses, necrotizing pneumonia, and empyema.

Other infections: Including brain abscesses, typically secondary to sinus or ear infections.

Diagnosis requires proper anaerobic sampling and laboratory techniques:

• Specimen collection: Deep tissue or pus samples with anaerobic transport
• Microscopy: Gram-negative pleomorphic rods
• Culture: Anaerobic growth with characteristic pigmentation
• Biochemical tests: Esculin positive, indole negative, bile sensitive
• Molecular methods: PCR or 16S rRNA sequencing for precise identification

Molecular diagnostics significantly improve detection sensitivity and specificity, especially in mixed infections.

Treatment depends on infection severity and location:

• Mild infections: Amoxicillin-clavulanate to cover β-lactamase producers
• Severe infections: Metronidazole or carbapenems (e.g., meropenem)
• Pelvic infections: Clindamycin due to good tissue penetration

Antimicrobial resistance is increasing. Over 80% of oral isolates produce β-lactamase, reducing the effectiveness of penicillin. While resistance to metronidazole remains low, emerging resistance trends warrant careful monitoring.

Preventive strategies focus on maintaining microbial balance and hygiene:

• Maintain good oral hygiene
• Avoid unnecessary antibiotic use
• Ensure proper sterilization of medical instruments

Effective sterilization methods include autoclaving (121°C, 15 min), boiling, or chemical disinfectants such as chlorine solutions or glutaraldehyde.