Molecular characterization of Streptococcus mutans strains containing the cnm gene encoding a collagen-binding adhesin

• Published in: Archives of oral biology 2010-01, Vol.55 (1), p.34-39
• Main Authors: Nakano, K, Nomura, R, Taniguchi, N, Lapirattanakul, J, Kojima, A, Naka, S, Senawongse, P, Srisatjaluk, R, Grönroos, L, Alaluusua, S, Matsumoto, M, Ooshima, T
• Format: Article
• Language: English
• Subjects: Adhesins, Bacterial - genetics; Advanced Basic Science; Blotting, Southern; Carrier Proteins - genetics; Clinical isolates; Collagen - metabolism; Collagen-binding adhesin; Dental Caries - microbiology; Dentistry; Finland; Gene Expression Regulation, Bacterial - physiology; Glucan-binding activity; Glucans - metabolism; Humans; Japan; Polymerase Chain Reaction; Protein Binding - genetics; Saliva - microbiology; Streptococcus mutans; Streptococcus mutans - genetics; Streptococcus mutans - isolation & purification; Streptococcus mutans - pathogenicity; Thailand
• ISSN: 0003-9969; 1879-1506
• DOI: 10.1016/j.archoralbio.2009.11.008

Abstract Objective Streptococcus mutans , known to be a major pathogen of dental caries, is also considered to cause infective endocarditis. Its 120-kDa Cnm protein binds to type I collagen, which may be a potential virulence factor. In this study, we characterized S. mutans clinical strains focusing on the cnm gene encoding Cnm. Design A total of 528 S. mutans strains isolated from Japanese, Finnish, and Thai subjects were investigated. Using molecular techniques, the distribution frequency of cnm -positive strains and location of the inserted cnm were analyzed. Furthermore, isogenic mutant strains were constructed by inactivation of the cnm gene, then their biological properties of collagen-binding and glucan-binding were evaluated. Southern hybridization of the genes encoding glucan-binding proteins was also performed. Results The distribution frequency of cnm -positive strains from Thai subjects was 12%, similar to that previously reported for Japanese and Finnish subjects. Furthermore, the location of insertion of cnm was the same in all cnm -positive clinical isolates. As for the cnm -inactivated mutant strains constructed from 28 clinical isolates, their collagen-binding activity was negligible. In addition, glucan-binding activity in the cnm -positive clinical isolates was significantly reduced and corresponded to a lack of gbpA encoding glucan-binding protein A. Conclusions Our results indicate that strains with cnm genes, the most crucial factor for the collagen-binding property of S. mutans , are detectable at similar frequencies over several different geographic locations. In addition, the common properties of these strains are a high level of collagen-binding activity and tendency for a low level of glucan-binding activity.