Implantation of Streptococcus mutans on tooth surfaces in man

Abstract

Streptomycin-resistant strains of Streptococcus mutans were implanted as adherent growth on artificial fissures (AF). A stock culture of strain E49 (serotype a) and human isolates of serotype c strains were each implanted in three subjects. The AF was retained in the occlusal surface of a tooth for 80-288 h, during which occlusal samples from the AF and salivary samples were regularly cultured, as well as AF itself when removed from the mouth. The streptomycin-resistant marker appeared stable in vitro and in vivo. Strain E49 failed to establish, as the colony-forming units (CFU) of this organism decreased with time in the AF to low or undetectable levels. At the same time, the AF became colonized by the indigenous flora including streptomycin-sensitive strains of Strep. mutans. The implanted serotype c strains of Strep. mutans seemed to establish; the CFU of these strains in the AF did not appreciably decrease with time in vivo. This suggests that serotype c strains possess a unique advantage over a stock culture of a serotype a strain in their ability to implant in the human mouth using the AF model. Although the implanted Strep. mutans strains were always found in the saliva when their numbers exceeded 105 CFU in the AF, they were rare when the level was below 105 CFU. In samples from the AF orifice, implanted Strep. mutans was only detected on 5 of 18 occasions, when these strains were demonstrably present within the AF.