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Pathology · single question

Streptococcus mutans is MOST associated with which role in the oral cavity?

  1. PRIMARY cariogenic bacterium — produces lactic acid and forms adherent plaque via glucan synthesis
  2. Primary periodontal pathogen
  3. Causes acute necrotizing ulcerative gingivitis (ANUG)
  4. Causes infective endocarditis from dental procedures
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Correct answer: A. PRIMARY cariogenic bacterium — produces lactic acid and forms adherent plaque via glucan synthesis

  • A. Correct. Streptococcus mutans is the PRIMARY CARIOGENIC (caries-causing) bacterium. Key virulence factors: (1) GLUCOSYLTRANSFERASES — produce glucans (sticky polymer) from sucrose, enabling plaque adherence, (2) Produces LACTIC ACID through fermentation, lowering plaque pH below 5.5 (critical pH for enamel demineralization), (3) Acid-tolerant (aciduric) — survives the acidic environment it creates, (4) Uses sucrose specifically.
  • B. Periodontal pathogens: P. gingivalis, T. forsythia, T. denticola (red complex), A. actinomycetemcomitans — not S. mutans.
  • C. ANUG is caused by Fusobacterium nucleatum, spirochetes (Treponema), Prevotella intermedia.
  • D. Infective endocarditis from dental procedures is caused by viridans streptococci (S. sanguinis, S. mitis) — a different group from S. mutans.

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