Bacteriocin production by Streptococcus milleri.

Bacteriocinlike activity was sought among 58 streptococcal strains using a deferred antagonism technique and 50 indicator strains. Antagonist production was generally increased by glucose supplementation of brain heart infusion agar and reduced by addition of calcium carbonate. Activity due to complete bacteriophage was excluded, as was toxic buildup of lactate, acetate, or ethanol. Hydrogen peroxide activity was responsible for all, or part, of antagonist activity in Streptococcus mutans tested and in nine strains of S. milleri. Virtually all isolates of S. milleri tested were sensitive to the bacteriocinlike activity of S. mutans NCTC 10832.