Objectives: We investigated the characteristics of Streptococcus mutans in the national culture collection from Korea. Twenty-nine (dental plaque, n=27; endodontic infections, n=1; blood, n=1) isolates were included in this study.
Methods: Antimicrobial susceptibilities were tested using the disk diffusion test. Multilocus sequence typing (MLST), serotyping, and collagen-binding genes were used for polymerase chain reaction (PCR) and direct sequencing. A collagen-binding (to assess the adhesion properties) assay was performed. S. mutanss demonstrated high susceptibility to antimicrobial agents. Differences in collagen-binding abilities of the cnm-positive and -negative groups were compared using the Mann-Whitney U test (P<0.05).
Results: MLST analyses revealed 25 sequence types (STs), 17 of which (ST213-ST229) contained new alleles. The strains were classified into four serotypes with the c type encompassing 79.3% of all strains, while the e, f, and k types representing 6.9% each. Analysis of the cnm and cbm genes, which encode the two surface adhesin components of S. mutanss, revealed three cnm-positive strains, each displaying greater adhesion ability than those of the cnm-negative strains.
Conclusions: This study highlights the presence of a wide variety of S. mutanss genotypes in Korea. These findings may provide useful information regarding the pathogenesis of infectious diseases, such as dental caries.

Keywords: Adhesion, Bacteremia, Collagen binding, MLST, Infection, Inflammation, Streptococcus mutans