Which microorganism is the primary etiologic agent classically implicated in the initiation of dental caries?

Streptococcus mutans is the primary cariogenic organism classically implicated in caries initiation, due to its strong acidogenic (acid-producing) and aciduric (acid-tolerant) properties along with its ability to synthesize extracellular polysaccharides that promote biofilm adhesion; Lactobacillus species become more prominent as established lesions progress.