Intraoral spread of Streptococcus mutans in man.

Streptomycin-resistant strains of Streptococcus mutans were reliably established in 3 subjects by the use of artifical fissures (AF) containing adherent growth of the Strep. mutans strain. The intraoral spread of these implanted Strep. mutans strains was monitored in the subjects while the AF was in situ and for up to 26 weeks after the AF was removed. During the 26 weeks, all tooth surfaces and saliva were repeatedly sampled. The implanted Strep. mutans spread to adjacent and antagonistic teeth only on the side of the dentition where the implantations were made. After establishment of a streptomycin-resistant strain in one subject, a sterile AF was inserted multiple times in the same occlusal surface, on which the implantations had previously been made. The sterile AF was colonized by local spread of Strep. mutans strains, as was shown by the relationship between the percentage of streptomycinresistant Strep. mutans to total Strep. mutans colony forming units (CFU) counts in the AF and the salivary flora. The streptomycin-resistant Strep. mutans represented 10.5-93.5 per cent of the total Strep. mutans CFUs in the AF, but only G-1.5 per cent of the Strep. mutans CFUs in the saliva during colonization of the AF. The intraoral establishment and spread of the implanted Strep. mutans seemed favoured by conditions present in subjects with high salivary concentrations of endogenous Strep. mutans strains and high caries experience, as expressed by the high number of filled tooth surfaces.