Infectivity and natural transmission of the bacterium Streptococcus mutans in monkeys (Macaca fascicularis) at different ages.

Oral inoculation of adolescent monkeys with laboratory strains of Streptococcus mutans resulted in only sporadic implantation. Oral colonization of all strains, except possibly one, was not enhanced by dietary sucrose compared with glucose nor by precleaning of accessible tooth surfaces. Infant animals were more susceptible to implantation by laboratory-maintained strains of Strep. mutans than adolescent or adult animals. This difference was magnified when in-vivo maintained Strep. mutans strains were used. Strep. mutans was readily acquired by uninfected adolescent animals from infected cage mates. Strep. mutans-free adolescent monkeys exhibited significant-salivary IgA and serum-IgG response to Strep. mutans antigen, possibly representing a cross-reaction to indigenous Streptococcus sanguis. Uninfected infant animals showed no salivary or serum response to Strep. mutans. There was no change in salivary IgA antibody to Strep. mutans in adolescent animals after implantation or in recipient animals after acquisition of Strep. mutans.