Mutans streptococci are the primary cariogenic agents, and Streptococcus mutans and Streptococcus sobrinus are believed to have the closest relationship with human caries.

• 变形链球菌属是目前公认的致龋菌，其中与人类龋病发生关系密切的是变形链球菌和远缘链球菌。