J Korean Acad Oral Health.  2012 Mar;36(1):1-6.

The comparison of the characteristics of Streptococcus mutans isolated from caries free and high caries children

  • 1Department of Preventive Dentistry, School of Dentistry, Kyungpook National University, Daegu, Korea. kbsong@knu.ac.kr
  • 2Department of Dental Hygiene, Ulsan College, Ulsan, Korea.


Streptococcus mutans (S. mutans) is the major causative bacteria in human dental decay. Most findings have shown that S. mutans are widely distributed in populations with moderate to high caries prevalence. However, observations have shown that S. mutans are also frequent in populations with low caries prevalence, as well. This study evaluated the relationship between the dental caries experience and the virulence factors of S. mutans, which are isolated from caries-free and high-caries individuals.
The dental caries experience states with the WHO diagnostic criteria, which were examined for children (aged 8 to 9 years) from two schools that are located in Daegu, Korea. A total of 22 caries-free (dfs+DFS=0) and 12 high-caries (dfs+DFS> or =14, ds+DS> or =9) were selected for this study. Dental plaque samples were obtained and incubated in MSB plate to culture S. mutans. After isolation and identification, the level of S. mutans, attachment ability, and streomicroscopy were analyzed.
The S. mutans counts and attachment ability were higher in the high-caries group than in the caries-free group (P<0.05). In addition, the colonies isolated from the caries-free group adhered less strongly to the Mitis Salivarius Bacitracin agar. There were less of the sticky substances from the surface of the S. mutans colonies in the caries-free group.
These results indicate that caries activity affected by the virulence not only the number of S. mutans.


Dental caries; Streptococcus mutans; Virulence
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