Neisseria and Streptococcus Reference Laboratory, Department for Microbiological Surveillance and Research, Statens Serum Institut, Artillerivej, Copenhagen, Denmark.
BMC Infect Dis. 2010 Sep 24;10:282. doi: 10.1186/1471-2334-10-282.
In 2007, Park et al. identified a novel serotype among Streptococcus pneumoniae serogroup 6 which they named serotype 6C. The aim of this study was to evaluate with the Neufeld test a novel S. pneumoniae serotype 6C type specific polyclonal antiserum. In addition, serotype 6C isolates found in Denmark in 2007 and 2008 as well as eight old original serotype 6A isolates were characterised.
In this study, 181 clinical Streptococcus pneumoniae isolates from Denmark 2007 and 2008 were examined; 96 isolates had previously been typed as serotype 6A and 85 as serotype 6B. In addition, eight older isolates from 1952 to 1987, earlier serotyped as 6A, were examined. Serotype 6C isolates were identified by PCR and serotyping with the Neufeld test using the novel type specific polyclonal antiserum, factor antiserum 6 d, in addition to factor antisera 6b, 6b* (absorbed free for cross-reactions to serotype 6C) and 6c. All antisera are commercially available and antiserum 6b obtained from the supplier after 1 January 2009 is antiserum 6b*. All serotype 6C isolates were further characterised using multi-locus sequence typing.
When retesting all 96 original serotype 6A isolates by PCR and the Neufeld test, 29.6% (24 of 81) of the invasive isolates in Denmark from 2007 and 2008 were recognised as serotype 6C. In addition, three of eight old isolates originally serotyped as 6A were identified to be serotype 6C. The oldest serotype 6C isolate was from 1962. The serotype 6C isolates belonged to eleven different sequence types (ST) and nine clonal complexes (CC), ST1692 (CC395), ST386 (CC386) and ST481 (CC460) were the predominant types.
We tested a novel polyclonal antiserum 6 d, as well as modified antiserum 6b*, provided a scheme for the serotyping of S. pneumoniae serogroup 6 using the Neufeld test and compared the serotyping method with PCR based methods. The two types of methods provided the same results. In future, it will, therefore, be possible to test also serotype 6C in accordance to the standard method for serotyping of S. pneumoniae recommended by WHO.Among all invasive isolates from Denmark 2007 and 2008, serotype 6C constituted 29.6% of the original serotype 6A isolates. The serotype 6C isolates were found to be diverse belonging to a number of different STs and CCs of which most have been observed in other countries previously. Serotype 6C is regarded as an "old" serotype being present among S. pneumoniae isolates in Denmark for at least 48 years. The genetic diversity of serotype 6C isolates and their genetic relationship to other serotypes suggested that serotype 6C strains may have arisen from several different independent recombination events involving different parental strains such as serotypes 6A, 6B, 23F and 4.
2007 年，Park 等人在肺炎链球菌 6 群中发现了一种新型血清型，将其命名为血清型 6C。本研究的目的是使用 Neufeld 试验评估一种新型肺炎链球菌 6C 型特异性多克隆抗血清。此外，还对丹麦 2007 年和 2008 年发现的血清型 6C 分离株以及 8 株旧的原始血清型 6A 分离株进行了特征描述。
本研究共检测了 181 株来自丹麦 2007 年和 2008 年的临床分离肺炎链球菌；96 株先前被分型为血清型 6A，85 株为血清型 6B。此外，还检测了 8 株来自 1952 年至 1987 年的旧分离株，先前被分型为 6A。通过 PCR 和 Neufeld 试验使用新型特异性多克隆抗血清（因子抗血清 6d），以及因子抗血清 6b、6b*（吸收后可与血清型 6C 交叉反应）和 6c 对血清型 6C 分离株进行鉴定。所有抗血清均可商购获得，2009 年 1 月 1 日之后从供应商处获得的抗血清 6b 为抗血清 6b*。所有血清型 6C 分离株均进一步通过多位点序列分型进行特征描述。
通过 PCR 和 Neufeld 试验重新检测所有 96 株原始血清型 6A 分离株，发现 2007 年和 2008 年丹麦侵袭性分离株中有 29.6%（81 株中的 24 株）被鉴定为血清型 6C。此外，8 株原始血清型为 6A 的分离株中有 3 株被鉴定为血清型 6C。最古老的血清型 6C 分离株来自 1962 年。血清型 6C 分离株属于 11 种不同的序列型（ST）和 9 个克隆群（CC），ST1692（CC395）、ST386（CC386）和 ST481（CC460）是主要类型。
我们测试了一种新型多克隆抗血清 6d，以及改良的抗血清 6b*，为使用 Neufeld 试验对肺炎链球菌 6 群进行血清分型提供了方案，并将该血清分型方法与基于 PCR 的方法进行了比较。两种方法提供了相同的结果。因此，将来也可以根据世界卫生组织推荐的肺炎链球菌血清分型标准方法来检测血清型 6C。在 2007 年和 2008 年丹麦所有侵袭性分离株中，血清型 6C 占原始血清型 6A 分离株的 29.6%。血清型 6C 分离株具有多样性，属于多个不同的 ST 和 CC，其中大多数之前在其他国家都有观察到。血清型 6C 被认为是一种“古老”的血清型，在丹麦肺炎链球菌分离株中已经存在至少 48 年。血清型 6C 分离株的遗传多样性及其与其他血清型的遗传关系表明，血清型 6C 菌株可能是由涉及不同亲本菌株（如血清型 6A、6B、23F 和 4）的几个不同的独立重组事件引起的。
