Abstract
Strains of Streptococcus mutans were isolated from plaque and softened dentin from 28 2-7 year old children. Serotypes and extracellular bacteriocin (mutacin)production were investigated. The total number of isolated strains was 288. Distribution of serotypes c, d, e, f and g were 71.2%,7.7%,14.9%,4.5% and 1.7%, respectively. Serotypes a and b were not isolated. The higher the caries activity and the higher the caries severity index the more serotypes other than c were isolated. Strains of 222 in 288,77.1%, produced mutacin against indicator strains S. sanguis ATCC 10556R, S. sanguis OMZ 9HR1, and S. salivarius HT9R by the stab culture method,33 strains (11.5%) against the same indicator strains by the drop assay method, and 30 strains (10.4%) against indicator strains S. mutans (serotypes a to g) by the drop assay method. There were three strains which produced mutacin against S. sanguis and S. salivarius but not against S. mutans. The medium influenced on mutacin production. Mutacin in the Todd Hewitt broth revealed the most bacteriocin-like activity against S. mutans. The second was the Tryptose phosphate broth, the third was the Brain Heart Infusion broth, and the last was the Trypticase Soy broth. Serotypes c and f of indicator S. mutans showed wide susceptibility to mutacin from various strains of S. mutans isolated from children, and serotype g showed narrow susceptibility.
