Shiga/verocytotoxins and Shiga/verotoxigenic Escherichia coli in animals.
Shiga/verocytotoxins and Shiga/verotoxigenic Escherichia coli in animals.
复制标题
动物中的志贺/维罗细胞毒素和志贺/维罗毒素大肠杆菌。
作者：
J. Mainil
Vero/Shiga毒素(VT/STX)具有A-B结构：A亚基携带酶活性，B亚基与膜受体(Gb3或Gb4)结合。VT/STX抑制靶真核细胞的蛋白质合成，主要是血管内皮细胞。VT/STX被细分为两个家族。VT1/STX1是一个与志贺氏菌STX相同的同源毒素家族。VT2/Stx2是一个更异质的毒素家族，与这种STX毒素关系更远。VT2/Stx2变异体可以通过聚合酶链式反应(PCR)和/或与单抗反应来区分。产生VT/STX的大肠埃希菌还根据有无其他特性被分为两大类：肠出血性大肠杆菌(EHEC)诱导形成附着/消失的病变，并携带编码特定溶血素(肠溶血素)的60MD质粒；Vero/志贺毒素大肠杆菌(VTEC/STEC)不显示这些特性。EHEC是从人类和反刍动物中分离出来的，特别是从小牛犊中分离出来的。它们与出血性小肠结肠炎及其在人类中的后遗症，溶血性尿毒症综合征(HUS)有关。VT/STX通过肠壁吸收后作用于肠粘膜下层和肾小球的血管内皮细胞，在粪便和HUS的血液发生中起作用。VTEC/STEC分离自仔猪、牛犊和人。在最近断奶的仔猪中，它们会引起水肿病，这是一种以皮下、肠系膜和脑内水肿为特征的肠毒血症，以神经紊乱为主要临床症状。水肿病是VT/STX作用于各器官血管内皮细胞的结果。在牛犊和人类中，VTEC/STEC在疾病中的作用存在争议，但它们可能与一些腹泻和HUS病例有关。O157：H7 EHEC存在于不同年龄段的健康牛身上，但对人类具有高度致病性，这一案例特别令人感兴趣。在动物中产生VT/STX的大肠杆菌感染的潜在的人畜共患方面将逐章详细介绍。通过接种疫苗预防这些感染是对这些致病菌研究未来的讨论的主题。
Vero/Shiga toxins (VT/Stx) have an A-B structure: the A subunit carries the enzymatic activity and the B subunit binds the toxin to the membrane receptor (Gb3 or Gb4). The VT/Stx inhibit protein synthesis in the target eucaryotic cells, mainly the endothelial cells of blood vessels. The VT/Stx are subdivided into two families. VT1/Stx1 is a homogeneous family of toxins identical to the Stx of Shigella dysenteriae. VT2/Stx2 is a more heterogeneous family of toxins more distantly related to this Stx toxin. The VT2/Stx2 variants can be distinguished by the polymerase chain reaction (PCR) and/or the reaction with monoclonal antibodies. The VT/Stx-producing Escherichia coli are also subdivided into two main groups on the basis of the presence or absence of additional properties: the enterohaemorrhagic E. coli (EHEC) induce the formation of attaching/effacing lesions and carry a 60 MD plasmid encoding a specific haemolysin (the enterohaemolysin); the vero/shiga-toxigenic E. coli (VTEC/STEC) do not show these properties. The EHEC are isolated from humans and ruminants, especially young calves. They are associated with haemorrhagic enterocolitis and its sequelae in humans, the haemolytic-uraemic syndrome (HUS). The VT/Stx play a role in the occurrence of blood in the faeces and in the HUS by their action on the endothelial cells of blood vessels in the intestinal submucosa and in the renal glomeruli, after resorption through the intestinal walls. The VTEC/STEC are isolated from piglets, calves and humans. In recently weaned piglets, they cause the oedema disease, an enterotoxaemia characterized by subcutaneous, mesenteric and cerebral oedemas, with nervous disorders as main clinical signs. The oedema disease is the consequence of the action of the VT/Stx on the endothelial cells of blood vessels in various organs. In calves and humans, the role in disease of VTEC/STEC is controversial, but they could be associated with some cases of diarrhoea and HUS. The case of the O157:H7 EHEC which are present in healthy cattle of various ages, but are highly virulent for humans is of special interest. The potential zoonotic aspect of VT/Stx-producing E. coli infections in animals is detailed chapter by chapter. Prophylaxis of these infections by vaccination is the subject of the discussion on the future of the research studies on these pathogenic bacteria.