Mutacin activity of strains isolated from children with varying levels of mutants streptococci and caries.

A total of 157 isolates of mutants streptococci from plaque and saliva of 94 children were studied for their serotypes, mutacin production, frequency and spectrum of activity. Of these isolates 71% were identified as serotype c and 22% as serotype e. Serotypes f, d and g, and one untypable strain made up about 7% of the isolates. More than one serotype was found in 13% of the children. Mutacin was produced by 83% of the isolates against one or more of the 14 indicator strains representing mutants streptococci. Streptococcus sanguis, Strep. oralis, Strep. gordonii, Strep. salivarius and Strep. pyogenes. Isolates that had a broad inhibitory spectrum also produced larger inhibition zones than isolates that inhibited fewer strains. When evaluating the effect of mutacin in vivo on plaque ecology, it was found that the counts of mutans streptococci or the proportion of mutans streptococci in the total streptococcal count of plaque did not differ between plaques containing strains that produced much mutacin and those with little production. The findings also failed to reveal an association between caries experience and mutacin activity.