WHO Collaborating Centre for Reference and Research on Escherichia and Klebsiella, Unit of Foodborne Bacteria and Typing, Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
J Clin Microbiol. 2012 Sep;50(9):2951-63. doi: 10.1128/JCM.00860-12. Epub 2012 Jul 3.
When Shiga toxin-producing Escherichia coli (STEC) strains emerged as agents of human disease, two types of toxin were identified: Shiga toxin type 1 (Stx1) (almost identical to Shiga toxin produced by Shigella dysenteriae type 1) and the immunologically distinct type 2 (Stx2). Subsequently, numerous STEC strains have been characterized that express toxins with variations in amino acid sequence, some of which confer unique biological properties. These variants were grouped within the Stx1 or Stx2 type and often assigned names to indicate that they were not identical in sequence or phenotype to the main Stx1 or Stx2 type. A lack of specificity or consistency in toxin nomenclature has led to much confusion in the characterization of STEC strains. Because serious outcomes of infection have been attributed to certain Stx subtypes and less so with others, we sought to better define the toxin subtypes within the main Stx1 and Stx2 types. We compared the levels of relatedness of 285 valid sequence variants of Stx1 and Stx2 and identified common sequences characteristic of each of three Stx/Stx1 and seven Stx2 subtypes. A novel, simple PCR subtyping method was developed, independently tested on a battery of 48 prototypic STEC strains, and improved at six clinical and research centers to test the reproducibility, sensitivity, and specificity of the PCR. Using a consistent schema for nomenclature of the Stx toxins and stx genes by phylogenetic sequence-based relatedness of the holotoxin proteins, we developed a typing approach that should obviate the need to bioassay each newly described toxin and that predicts important biological characteristics.
当产志贺样毒素大肠杆菌 (STEC) 菌株成为人类疾病的病原体时，人们鉴定出了两种毒素：志贺毒素 1 型 (Stx1)（几乎与痢疾志贺菌 1 型产生的志贺毒素相同）和免疫上不同的 2 型 (Stx2)。随后，人们对许多表达毒素的 STEC 菌株进行了特征描述，这些毒素的氨基酸序列存在差异，其中一些赋予了它们独特的生物学特性。这些变体被分为 Stx1 型或 Stx2 型，通常会被赋予一个名称，以表明它们在序列或表型上与主要的 Stx1 或 Stx2 型不完全相同。由于在毒素命名方面缺乏特异性或一致性，导致 STEC 菌株的特征描述非常混乱。由于某些 Stx 亚型与严重感染后果相关，而其他亚型则不然，因此我们试图更好地定义主要 Stx1 和 Stx2 型中的毒素亚型。我们比较了 285 种有效 Stx1 和 Stx2 序列变体的相关性水平，并确定了每个 Stx/Stx1 三型和 Stx2 七型共有的特征序列。我们开发了一种新颖的、简单的 PCR 亚型分型方法，对 48 株原型 STEC 菌株进行了独立测试，并在六个临床和研究中心进行了改进，以测试 PCR 的重现性、敏感性和特异性。通过对全毒素蛋白的系统发育序列相关性对 Stx 毒素和 stx 基因进行基于命名法的命名，并基于 Stx 毒素和 stx 基因的命名法，我们开发了一种分型方法，该方法应该避免对每个新描述的毒素进行生物测定的需要，并且可以预测重要的生物学特征。
