Which bacteria are found in Periodontitis?

Obligate anaerobic Gram-negative bacteria (A) predominate in periodontitis. The subgingival microbiome shifts from Gram-positive aerobic species (health) to Gram-negative anaerobic species as periodontal pockets deepen (anaerobic environment).

Red complex (most virulent periodontitis pathogens):
• Porphyromonas gingivalis — Gram-neg, obligate anaerobe
• Tannerella forsythia — Gram-neg, obligate anaerobe
• Treponema denticola — Gram-neg spirochete, obligate anaerobe

Orange complex: Fusobacterium nucleatum, Prevotella intermedia, Campylobacter rectus

• Aggregatibacter actinomycetemcomitans (Gram-neg, facultative): associated with aggressive/localized periodontitis (molar-incisor pattern).