Molecular and clinical analyses of the gene encoding the collagen-binding adhesin of Streptococcus mutans

Abstract

Streptococcus mutans is a known pathogen of dental caries and its major cell surface antigens have been widely investigated. Recently, an approximately 120 kDa Cnm protein with binding properties to type I collagen was identified, and its encoding gene (cnm) cloned and sequenced. In the present study, we sequenced cnm from 47 different clinical S. mutans strains and found that the nucleotide alignment of the collagen-binding domain was well conserved. We devised a PCR method for identifying the cnm gene, examined the prevalence of cnm-positive S. mutans strains in various mother-child groups, and assessed the significance of such strains for transmission and dental caries. The detection rate of cnm-positive strains was significantly lower in strains isolated from Japanese children in the 2000s (8.0 %) as compared to those isolated in the 1980s (15.8 %) (P,0.05). Furthermore, the presence of S. mutans possessing cnm in salivary specimens collected from 55 S. mutans-positive mother-child pairs was 40 and 32.7 % in the mothers and children, respectively. The frequency of cnm-positive children whose mothers were also positive was 72 %, which was significantly higher than that of cnm-positive children with negative mothers (P,0.0001, odds ratio 17.5). In addition, clinical parameters indicating dental caries were significantly increased in children with cnm-positive S. mutans in saliva (n513), as compared to those with cnm-negative S. mutans (n515) and S. mutans-negative children (n520) (P,0.01). These results indicate that cnm-positive S. mutans strains are closely correlated with dental caries, while vertical transmission in cnm-positive mother-child pairs was also demonstrated.

Multilocus sequence typing analysis of Streptococcus mutans strains with the cnm gene encoding collagen-binding adhesin

“…We found that the distribution of the cnm gene in S. mutans from Thai subjects was highest in serotype f (54.5 %). Such distribution was also observed in S. mutans strains from Japanese and Finnish people (Nakano et al, 2007;Nomura et al, 2009). These results thus confirmed the association between serotype f and the presence of the cnm gene in S. mutans.…”

“…In addition, the Cnm protein was proved to be necessary for invasion of human coronary artery endothelial cells (Abranches et al, 2011). The distribution of the strains with the cnm gene has previously been reported in two populations, Japanese and Finnish people, in which S. mutans with minor serotypes, f and k, showed high proportions of the gene (Nakano et al, 2007;Nomura et al, 2009). Subsequently, the presence of strains with the cnm gene was reported in 6 of 50 strains from 50 Thai subjects (Nakano et al, 2010).…”

Roles of Oral Bacteria in Cardiovascular Diseases — From Molecular Mechanisms to Clinical Cases: Cell-Surface Structures of Novel Serotype k Streptococcus mutans Strains and Their Correlation to Virulence

“…It was reported that strain TW295 lacks expression of PA and GbpA and that strain TW871 lacks GbpA expression and has an altered expression of GbpC. On the other hand, those strains possess cnm genes, which are related to binding to type I collagen, although their distribution frequency in oral strains is estimated to range from 10% to 20% (14). These findings led us to speculate that alterations of cell surface antigens would be frequently identified in serotype-k strains.…”

“…Cell surface antigens have been shown to be important for phagocytotic susceptibility of S. mutans , and a defect of PA or Gbps resulted in resistance to phagocytosis by polymorphonuclear leukocytes in vitro, which caused a greater duration of bacteremia and systemic inflammation in vivo in a rat bacteremia model (27,28). As for the virulence of S. mutans in infective endocarditis, strains with Cnm are considered to have advantages in regard to their ability to attach to exposed endothelial collagen, and we recently found that the detection frequency of strains with the cnm gene was significantly higher in a serotype-k group as compared to groups categorized by the major serotypes c and e groups (14).…”

“…Recently, the 120-kDa cell surface collagen-binding adhesin (Cnm protein) and its coding gene cnm were also characterized (13). The prevalence of S. mutans strains with cnm in the oral cavity was demonstrated to range from 10% to 20% and its presence was shown to be correlated to dental caries, as the exposed structure of a tooth in the process of dental caries development contains type I collagen (14). Since Cnm protein was found to bind to immobilized collagen and laminin, it is considered to be a possible etiologic factor in S. mutans -related heart valve disorders.…”