The stability of Streptococcus mutans populations in the dental plaque of monkeys (Macaca fascicularis)

The Streptococcus mutans populations in the dental plaque of two groups of monkeys were examined. In the first group of 17 monkeys the proportion of Strep. mutans in the dental plaque increased when the monkeys were fed a cariogenic high sucrose (CHS) diet. The same predominant Strep. mutans serotypes were present in the plaque of these monkeys 12 and 25 months after the change to the CHS diet. A second group of 22 monkeys was caged in two communes. As a result of a change to the CHS diet one commune harboured a plaque flora in which Strep. mutans serotype e strains predominated and the second commune harboured a plaque flora in which Strep. mutans serotypes c and h predominated. On the basis of the results from these 39 monkeys three types of Strep. mutans populations were identified: (i) serotype e dominated; (ii) serotype c dominated; and (iii) serotypes c and h in varying proportions. It was not possible to predict which Strep. mutans population would become established in a given group of monkeys. Attempts to demonstrate transmission of Strep. mutans serotypes between pairs and larger groups of monkeys caged together were not successful over periods of up to 36 weeks. The implications of these observations on the use of monkeys as a model of human dental caries is discussed.