Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028 Lisboa, Portugal.
Eur J Clin Microbiol Infect Dis. 2013 Jan;32(1):115-25. doi: 10.1007/s10096-012-1726-3. Epub 2012 Aug 31.
The profiling of the superantigen (SAg) encoding genes has been frequently used as a complementary typing method for group A streptococci (GAS), but a confusing gene nomenclature and a large diversity of primers used in screening has led to some conflicting results. The aim of this work was to develop a polymerase chain reaction (PCR) method capable of efficiently amplifying all the known allelic variants of these genes, and to evaluate the congruence of this methodology with other commonly used molecular typing methods. The presence of the 11 known SAg genes and two other exotoxin-encoding genes (speB and speF) was tested in a collection of 480 clinical GAS isolates, using two multiplex PCR reactions. The SAg gene profile was compared with other typing methods. Four naturally occurring deletions involving the genes speB, speF, and rgg were characterized, two of which were found among invasive isolates. The absence of the chromosomally encoded genes speG and smeZ was supported by Southern blot hybridization and associated with specific GAS lineages, while the presence of phage-encoded genes was more variable. Positive associations between SAg genes or between SAg profiles and emm types or pulsed-field gel electrophoresis (PFGE) clusters were observed. The results suggest that the SAg profile diversifies faster than other properties commonly used for molecular typing, such as emm type and multilocus sequence typing (MLST) sequence types (STs), and can be a useful complement in GAS molecular epidemiology. Still, the short-term stability of the SAg gene profile among prevalent genetic lineages may largely explain the observed associations between SAg genes.
超抗原（SAg）编码基因的分析已被广泛用于 A 组链球菌（GAS）的补充分型方法，但由于基因命名混乱和筛选中使用的大量引物，导致了一些相互矛盾的结果。本研究旨在开发一种聚合酶链反应（PCR）方法，能够有效地扩增这些基因的所有已知等位变体，并评估该方法与其他常用分子分型方法的一致性。使用两个多重 PCR 反应，在 480 株临床 GAS 分离株中检测了 11 个已知的 SAg 基因和另外两个外毒素编码基因（speB 和 speF）的存在。将 SAg 基因谱与其他分型方法进行比较。鉴定了涉及基因 speB、speF 和 rgg 的四个自然发生的缺失，其中两个缺失存在于侵袭性分离株中。染色体编码基因 speG 和 smeZ 的缺失通过 Southern 印迹杂交得到支持，并与特定的 GAS 谱系相关，而噬菌体编码基因的存在则更为多变。观察到 SAg 基因之间或 SAg 谱与 emm 型或脉冲场凝胶电泳（PFGE）聚类之间存在阳性关联。结果表明，SAg 谱的多样化速度比其他常用于分子分型的特性（如 emm 型和多位点序列分型（MLST）序列型（ST））更快，并且可以在 GAS 分子流行病学中作为有用的补充。然而，在流行的遗传谱系中，SAg 基因谱的短期稳定性可能在很大程度上解释了 SAg 基因之间观察到的关联。
