Which of the following bacteria is most commonly associated with dental caries due to acid production?

• A. Streptococcus mutans
• B. Streptococcus sanguinis
• C. Veillonella parvula
• D. Actinomyces naeslundii

Answer: (A)

Acid production by plaque bacteria is a key driver of dental caries. Streptococcus mutans stands out because it is highly acidogenic and aciduric, meaning it rapidly ferments sugars to lactic acid and can continue thriving even as the local pH drops. It also forms robust biofilms by producing extracellular polysaccharides from sucrose, which helps it adhere to the tooth surface and create a sticky, protective plaque matrix. This combination of strong adherence, rapid acid production, and tolerance to low pH makes S. mutans the principal organism associated with caries initiation and progression. In comparison, Streptococcus sanguinis is more of an early, less cariogenic colonizer; Veillonella parvula consumes lactate produced by other bacteria rather than generating acid itself; and Actinomyces naeslundii contributes to plaque and root surface associations but is not the main acid-producing driver of classic caries.