Periodontics · single question
When examining a patient for chronic periodontitis, which of the following organisms would NOT typically be found in the diseased site?
Show answer and explanation
Correct answer: B. Streptococcus mutans
Streptococcus mutans is the primary organism associated with dental caries, not periodontitis. Chronic periodontitis is associated with anaerobic gram-negative organisms including P. gingivalis, T. denticola, and T. forsythia (the 'red complex'). S. mutans is a facultative anaerobe found in supragingival biofilm and is not a periodontal pathogen.
- A. P. gingivalis is a classic red complex organism and major periodontal pathogen — it would be present in chronic periodontitis sites.
- B. CORRECT. Streptococcus mutans is the primary caries pathogen, not a periodontal pathogen. It thrives in supragingival biofilm at low pH and is NOT found in subgingival periodontal pockets.
- C. Tannerella forsythia (formerly Bacteroides forsythus) is the third member of the red complex and is strongly associated with chronic periodontitis.
- D. Treponema denticola is part of the red complex and is a key pathogen in chronic periodontitis.