Incidence of bacteriocinogeny among fresh isolates of Streptococcus mutans.

Among 139 Streptococcus mutans fresh isolates tested, using the deferred-antagonism test and Streptococcus sanguis Ny 101 as the indicator strain, we observed that the frequency of detection of inhibition zones was reduced by 19% (from 53 to 34%) when arginine (1%) was used in the overlay agar. Among pigmented strains, the frequency of mutacin-like production was 70%. The frequency with which inhibition zones were detected varied from 7 to 91%, depending on the indicator strain used. These results indicate that the ability to detect the presence of mutacin-like substances varies widely and is dependent to a great extent on the methodology used.