S. Mitis Species By Housekekeeping Gene Sequencing

我们已经向NIAID提交了一项倡议，以开发生物恐怖主义细菌制剂和其他密切相关生物的关键基因靶标的遗传序列库。这些基因靶点包括16S核糖体RNA基因和基本管家基因(HKG)。作为这种方法的证据，我们选择了绿色链球菌组，因为它们长期以来很难通过传统的表型方法进行识别。绿色链球菌是一组革兰氏阳性细菌，构成了人类口腔和胃肠道驻留菌群的一部分。它们偶尔会被发现为一过性菌血症的原因，特别是在牙科手术后。这组链球菌已成为亚急性细菌性心内膜炎的重要病原体之一，可导致严重的心脏瓣膜损害。绿色链球菌至少由22个种组成，目前分为5个亚组：假单胞菌、变形菌、唾液菌和牛链球菌。Mitis群链球菌是导致人类疾病的最常见的绿色链球菌。在过去的几十年里，随着基于分子的方法的出现，绿色链球菌的重新分类一直在演变，有时是令人困惑的。含糊不清的原因之一是，用于鉴定临床实验室中分离的大多数细菌的常规生化测试往往不能在物种层面提供明确的鉴定，而且还可能误认这一组的成员。最近提出了一种利用16S rDNA基因序列鉴定细菌病原体的新方法。然而，这项技术在一些密切相关的生物中并没有帮助，这些生物的16S基因序列几乎相同。我们已经开始探索一套新的精选HKG，可能显示绿色链球菌成员之间的DNA碱基差异显著，特别是MITS组生物。与16S rDNA测序相比，这些HKG可能会产生更好的鉴定系统。

We have submitted an initiative to NIAID for the development of a library of genetic sequences for critical gene targets for bacterial agents of bioterrorism and other closely related organisms. These gene targets include 16S ribosomal RNA genes and essential housekeeping genes (HKG). As a proof of this approach, we have selected viridans group streptococci because they have long been difficult to identify by traditional phenotypic methods. The viridans streptococci are a group of gram-positive bacteria that constitute part of the resident flora in the human oral cavity and gastrointestinal tract. They can occasionally be found as a cause of transient bacteremia, especially following dental procedures. This group of streptococci has become one of the important causative agents of subacute bacterial endocarditis that can result in serious damage of heart valves. Viridans streptococci are composed of at least 22 species, which are currently divided into 5 subgroups: mitis, anginosus, mutans, salivarius, and bovis. Mitis group streptococci are the most common viridans streptococci responsible for diseases in humans. In the past decades, with the emergence of molecular-based methods, re-classification of viridans streptococci has been evolving and is sometimes confusing. One of the reasons for the ambiguity is that conventional biochemical tests used to identify most of the bacteria isolated in the clinical laboratory often do not provide definitive identification at the species level, and may also misidentify members of this group. A new approach for the identification of bacterial pathogens using 16S rDNA gene sequences has been recently introduced. However, this technique has not been helpful in some closely related organisms that have nearly identical sequences in their 16S genes. We have begun exploring a new set of selected HKG that may show a significant number of DNA base differences among members of the viridans streptococci, specifically the mitis group organisms. In comparison to 16S rDNA sequencing, these HKG may result in a better identification system for these organisms.