Streptococcus milleri (Guthof) and Streptococcus mutans in the mouths of infants before and after tooth eruption.

Group I infants had no primary teeth, group II had 2–8 primary teeth, and group III had all primary teeth erupted. Streptococcus sanguisand Streptococcus salivarius were analysed as reference organisms. Strep. milleri was detected in samples taken from 6 of the 21 infants in group I, in 9 of the 16 in group II, and in 15 of the 16 infants in group III. The prevalence of Strep. milleri was similar to that of Strep, sanguis, suggesting that the presence of teeth favours the establishment of Strep, milleri. Small numbers of Strep.mutans were observed in all 3 groups. The low prevalence and proportions of Strep, milleri,Strep. sanyuis and Strep. mutans in predentate infants suggest that they are not indigenous to the mouth.