Periodontics · single question
Which type of bacteria predominates in chronic periodontitis?
Show answer and explanation
Correct answer: C. Anaerobic Gram-negative bacteria
Chronic periodontitis is associated with a complex subgingival biofilm dominated by anaerobic Gram-negative bacteria. The 'red complex' bacteria (Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola) are the primary pathogens. These are anaerobic, Gram-negative organisms that thrive in the oxygen-depleted environment of deep periodontal pockets.
- A. Incorrect. Aerobic Gram-positive cocci (like Streptococcus) predominate in HEALTH and early gingivitis, not in established chronic periodontitis.
- B. CORRECT. Chronic periodontitis is characterized by anaerobic Gram-negative bacteria (P. gingivalis, T. forsythia, T. denticola — the 'red complex') in deep pockets.
- C. Incorrect. Gram-positive rods are more associated with health or early disease states.
- D. Incorrect. Spirochetes (Treponema) are present in periodontitis, but they are Gram-negative and anaerobic — not 'motile cocci.' Spirochetes are a subset, not the primary classification.