Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
Arch Oral Biol. 2010 Jan;55(1):34-9. doi: 10.1016/j.archoralbio.2009.11.008. Epub 2009 Dec 14.
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.
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.
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.
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.
众所周知，变异链球菌是龋齿的主要病原体，也被认为会引起感染性心内膜炎。其 120kDa 的 Cnm 蛋白与 I 型胶原结合，这可能是一种潜在的毒力因子。在本研究中，我们对变异链球菌临床株进行了特征分析，重点是编码 Cnm 的 cnm 基因。
共研究了来自日本、芬兰和泰国受试者的 528 株变异链球菌株。利用分子技术，分析了 cnm 阳性菌株的分布频率和插入 cnm 的位置。此外，还构建了 cnm 基因失活的同基因突变株，然后评估了其胶原结合和葡聚糖结合的生物学特性。还对编码葡聚糖结合蛋白的基因进行了 Southern 杂交。
来自泰国受试者的 cnm 阳性菌株的分布频率为 12%，与之前报道的日本和芬兰受试者相似。此外，所有 cnm 阳性临床分离株的插入位置相同。对于从 28 株临床分离株构建的 cnm 失活突变株，其胶原结合活性可忽略不计。此外，cnm 阳性临床分离株的葡聚糖结合活性显著降低，与缺乏编码葡聚糖结合蛋白 A 的 gbpA 相对应。
我们的结果表明，具有 cnm 基因的菌株在几个不同的地理位置以相似的频率检测到，这是 S. mutans 胶原结合特性的最关键因素。此外，这些菌株的共同特性是具有高水平的胶原结合活性和低水平的葡聚糖结合活性的趋势。
