Nakano Kazuhiko, Lapirattanakul Jinthana, Nomura Ryota, Nemoto Hirotoshi, Alaluusua Satu, Grönroos Lisa, Vaara Martti, Hamada Shigeyuki, Ooshima Takashi, Nakagawa Ichiro
Departments of Pediatric Dentistry, Osaka University Graduate School of Dentistry, 1-8 Yamada-oka, Suita, Osaka 565-0871, Japan.
J Clin Microbiol. 2007 Aug;45(8):2616-25. doi: 10.1128/JCM.02343-06. Epub 2007 Jun 13.
Streptococcus mutans is the major pathogen of dental caries, a biofilm-dependent infectious disease, and occasionally causes infective endocarditis. S. mutans strains have been classified into four serotypes (c, e, f, and k). However, little is known about the S. mutans population, including the clonal relationships among strains of S. mutans, in relation to the particular clones that cause systemic diseases. To address this issue, we have developed a multilocus sequence typing (MLST) scheme for S. mutans. Eight housekeeping gene fragments were sequenced from each of 102 S. mutans isolates collected from the four serotypes in Japan and Finland. Between 14 and 23 alleles per locus were identified, allowing us theoretically to distinguish more than 1.2 x 10(10) sequence types. We identified 92 sequence types in these 102 isolates, indicating that S. mutans contains a diverse population. Whereas serotype c strains were widely distributed in the dendrogram, serotype e, f, and k strains were differentiated into clonal complexes. Therefore, we conclude that the ancestral strain of S. mutans was serotype c. No geographic specificity was identified. However, the distribution of the collagen-binding protein gene (cnm) and direct evidence of mother-to-child transmission were clearly evident. In conclusion, the superior discriminatory capacity of this MLST scheme for S. mutans may have important practical implications.
变形链球菌是龋齿（一种生物膜依赖性传染病）的主要病原体，偶尔也会引发感染性心内膜炎。变形链球菌菌株已被分为四种血清型（c、e、f和k）。然而，关于变形链球菌群体，包括变形链球菌菌株之间的克隆关系，以及与导致全身性疾病的特定克隆的关系，我们了解得还很少。为了解决这个问题，我们开发了一种用于变形链球菌的多位点序列分型（MLST）方案。从日本和芬兰收集的102株来自四种血清型的变形链球菌分离株中，对八个管家基因片段进行了测序。每个位点鉴定出14至23个等位基因，理论上使我们能够区分超过1.2×10¹⁰种序列类型。在这102株分离株中我们鉴定出92种序列类型，表明变形链球菌包含一个多样化的群体。血清型c菌株在系统发育树中广泛分布，而血清型e、f和k菌株则分化为克隆复合体。因此，我们得出结论，变形链球菌的祖先菌株是血清型c。未发现地理特异性。然而，胶原结合蛋白基因（cnm）的分布以及母婴传播的直接证据是明显的。总之，这种用于变形链球菌的MLST方案的卓越鉴别能力可能具有重要的实际意义。
