Prevalence of Streptococcus mutans harboring the cnm gene encoding cell surface protein Cnm in Japanese children

Dental caries is a highly prevalent infectious disease primarily caused by the pathogenic bacterium Streptococcus mutans, which has also been associated with systemic disease. A 120-kDa collagen-binding protein (Cnm) produced by S. mutans contributes to cardiovascular disease pathogenicity. Few studies have addressed the current prevalence of S. mutans and the cnm gene in Japanese children or examined caries pathology in relation to cnm presence. Here, we investigated the prevalence of S. mutans and the distribution of cnm-positive S. mutans among 490 children who visited two university hospitals in Japan. The caries experience index (dmft/DMFT) was calculated, and the collagen-binding ability of cnm-positive S. mutans strains was assessed. S. mutans was isolated from the oral cavities of 158 patients (36.8%); 10.1% (16/158) harbored cnm-positive S. mutans. When caries experience indices were compared across dentitions, patients harboring cnm-positive strains had significantly higher dmft/DMFT scores than those with cnm-negative strains (P < 0.05). Additionally, a positive correlation was observed between the collagen-binding capacity of cnm-positive S. mutans and the dmft/DMFT score (r = 0.601, P < 0.05). These findings suggest that cnm contributes to caries progression through collagen-mediated adherence to tooth surfaces. The presence of cnm-positive S. mutans may represent a risk factor for increased caries susceptibility in children.