Dental location of Streptococcus mutans and Streptococcus sobrinus in humans harboring both species

The distribution and prevalence of Streptococcus mutans and Streptococcus sobrinus were determined in plaque samples from the cervical areas of all buccal, lingual and approximal tooth surfaces and from the fissures of all occlusal sites in 40 subjects harboring both species. S. mutans was detected more often and in higher numbers than S. sobrinus. There were more teeth detected with S. mutans only than with S. sobrinus only. Most teeth harbored both of these mutans streptococci species, indicating a positive association. The highest numbers of CFU for both species were detected on the molars, with the lowest incidence on the anterior teeth. The presence of S. mutans was relatively similar on all teeth tested, while the presence of S. sobrinus was relatively higher on the molars compared to the anterior teeth. S. mutans and S. sobrinus were found to colonize the buccal surfaces in almost equal numbers. On all other surfaces, S. mutans was detected more frequently or in higher numbers compared to S. sobrinus. No significant differences could be found in the relative proportions of S. mutans and S. sobrinus between sound, decayed or filled tooth surfaces.