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

• Main Authors: K. Nakano, R. Nomura, N. Taniguchi, J. Lapirattanakul, A. Kojima, S. Naka, P. Senawongse, R. Srisatjaluk, L. Grönroos, S. Alaluusua, M. Matsumoto, T. Ooshima
• Other Authors: Osaka University
• Format: Article
• Published: 2018
• Subjects: Biochemistry, Genetics and Molecular Biology; Dentistry; Medicine
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/28843
• Institution: Mahidol University

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. © 2009 Elsevier Ltd. All rights reserved.