Primary oral infection of infants with Streptococcus mutans

Strep. mutans was not detected in 16 normal predentate infants, but was isolated from $\text{3}\text{43}$ infants with 1 to 5 primary incisor teeth and $\text{12}\text{42}$ infants with 6 to 8 incisors. The salivary level of Strep. mutans was determined for the 42 mothers of the infants with only 6 to 8 incisors. The difference in the distribution of the salivary levels of Strep. mutans within the maternal populations of infected versus non-infected infants was statistically significant (p = 0.03). Ten mothers harboured greater than 10⁵ colony-forming units (CFUs) of Strep. mutans per ml. saliva. The organism was detected in 6 of their infants. Of 13 mothers with levels less than 10³ CFUs per ml. saliva only 2 of their infants harboured the organism.