Department of Oral Microbiology, Faculty of Dentistry, Mahidol University, Bangkok 10400, Thailand.
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan.
J Med Microbiol. 2011 Nov;60(Pt 11):1677-1684. doi: 10.1099/jmm.0.033415-0. Epub 2011 Jun 16.
Streptococcus mutans is one of the oral pathogens associated with infective endocarditis (IE). With respect to bacterial binding ability to the extracellular matrix, the Cnm protein, a cell surface collagen-binding adhesin of S. mutans, is known as one of the possible virulence factors with regard to IE. In this study, we aimed to determine the distribution of the cnm gene, which encodes Cnm, in a large number of clinical isolates of S. mutans from Thai subjects. Then, the cnm-positive strains were classified using a multilocus sequence typing (MLST) scheme, which we constructed previously. In addition, the data were analysed together with our previous MLST data of cnm-positive strains from Japan and Finland in order to evaluate the clonal relationship among S. mutans strains harbouring the cnm gene. The cnm gene was detected in 12.4 % of all 750 Thai isolates, and serotype f showed the highest rate of detection (54.5 %). According to the MLST data, two clonal complex groups were revealed as the important clones related to cnm-positive S. mutans from various origins of isolation. Moreover, the collagen-binding properties of S. mutans strains with the cnm gene were significantly greater than those of strains without the gene, although four cnm-negative strains classified into two sequence types (STs), ST110 and ST136, showed extremely high collagen-binding rates suggesting the presence of additional genes involved with collagen binding in these STs. Taken together, these results provided information on both epidemiological as well as evolutional aspects of S. mutans possessing the cnm gene.
变形链球菌是与感染性心内膜炎（IE）相关的口腔病原体之一。就细菌与细胞外基质的结合能力而言，Cnm 蛋白是变形链球菌表面的一种细胞表面胶原蛋白结合黏附素，被认为是与 IE 相关的可能毒力因子之一。在本研究中，我们旨在确定 cnm 基因（编码 Cnm）在大量来自泰国受试者的变形链球菌临床分离株中的分布。然后，我们使用之前构建的多位点序列分型（MLST）方案对 cnm 阳性菌株进行分类。此外，我们分析了这些数据以及来自日本和芬兰的 cnm 阳性菌株的先前 MLST 数据，以评估携带 cnm 基因的变形链球菌菌株之间的克隆关系。在所有 750 株泰国分离株中，检测到 cnm 基因的比例为 12.4%，其中血清型 f 的检出率最高（54.5%）。根据 MLST 数据，两个克隆复合体群被揭示为与来自不同分离源的 cnm 阳性变形链球菌相关的重要克隆。此外，具有 cnm 基因的变形链球菌菌株的胶原蛋白结合特性明显大于没有该基因的菌株，尽管 4 株 cnm 阴性菌株分为 2 种序列型（ST），ST110 和 ST136，显示出极高的胶原蛋白结合率，表明这些 ST 中存在其他与胶原蛋白结合相关的基因。综上所述，这些结果提供了有关携带 cnm 基因的变形链球菌的流行病学和进化方面的信息。
