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Periodontics · single question

Which microbiological pattern is characteristic of the subgingival flora in aggressive (molar-incisor pattern) periodontitis?

  1. A predominance of three or more strict anaerobes and facultative anaerobes
  2. Two strictly aerobic species
  3. Predominantly aerobic gram-positive cocci
  4. A single strictly anaerobic species
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Correct answer: A. A predominance of three or more strict anaerobes and facultative anaerobes

  • A. Correct. Established periodontal lesions harbour a POLYMICROBIAL consortium dominated by anaerobes. Socransky's RED COMPLEX — Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola — is most strongly associated with disease severity, while Aggregatibacter actinomycetemcomitans (a facultative anaerobe) is classically linked to localised aggressive periodontitis. The general shift with disease progression is from gram-positive aerobic cocci in health toward gram-negative anaerobic rods and spirochaetes in disease.
  • B. Strict aerobes do not dominate a deep, oxygen-depleted subgingival pocket.
  • C. Gram-positive aerobic cocci characterise HEALTHY supragingival plaque, not the diseased pocket.
  • D. A monomicrobial picture does not reflect the polymicrobial reality of periodontal disease.

Note: 'Three or more strict anaerobes' is the best available option, but note A. actinomycetemcomitans — the organism most classically tied to aggressive periodontitis — is a FACULTATIVE, not strict, anaerobe. The examinable principle is the polymicrobial anaerobic shift.

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