Universidad de Buenos Aires, Facultad de Ciencias Veterinarias, Cátedra de Microbiología. Av. Chorroarín 280, (C1427CWO) Buenos Aires, Argentina.
Servicio Fisiopatogenia, Instituto Nacional de Enfermedades Infecciosas-ANLIS "Dr. Carlos G. Malbrán". Av. Vélez Sarsfield 563, (1281) Buenos Aires, Argentina.
Vet Microbiol. 2018 Feb;215:29-34. doi: 10.1016/j.vetmic.2017.12.006. Epub 2017 Dec 9.
Shiga toxin-producing Escherichia coli (STEC) is th etiological agent of gastrointestinal diseases as haemorrhagic colitis and haemolytic-uraemic syndrome (HUS). Shiga toxin (Stx) is the main virulence factor. There are two types, Stx1 and Stx2, and several subtypes. Other virulence factors are involved in pathogenesis. While O157:H7 is the predominant serotype, at present non-O157 STEC strains are increasingly recognized as foodborne pathogens worldwide. In Argentina, STEC O174 stands out as an emerging pathogen and is one of the four most prevalent non-O157 STEC serogroups. The aim of this study was to characterize 41 O174:[H21, H28] STEC strains isolated from animals, food, and humans. Isolates were characterized by stx genotyping, adhesion factors (afaC, eae, iha, lpf, saa, and toxB), additional toxins (cdtV, ehxA, subA) and clonal relationship by pulsed-field gel electrophoresis (PFGE). Among 30 O174:H21 strains, the most prevalent stx subtype was stx (56.7%), and among 11 O174:H28 strains, the most prevalent was stx (90.9%). Regarding virulence factors, all strains were positive for afaC gene and negative for eae and toxB genes. In O174:H21, the frequency of additional factors was lpf (96.6%), iha (83.3%), ehxA and saa (10%), and subA (3.3%), meanwhile in O174:H28 strains the frequency was iha and subA (100%), lpf (90.9%), ehxA and saa (90.9%), and cdtV (9.09%). By Xbal-PFGE, 29 patterns were established with 64.01% similarity and three clusters were detected. Given the fact that the O174 serogroup is a local emergent, it is important to study the virulence profiles to understand its potential pathogenicity.
产志贺毒素大肠杆菌（STEC）是引起胃肠道疾病（如出血性结肠炎和溶血尿毒综合征（HUS））的病原体。志贺毒素（Stx）是主要的毒力因子。它有两种类型，Stx1 和 Stx2，以及几种亚型。其他毒力因子也参与了发病机制。虽然 O157:H7 是主要血清型，但目前，非 O157 STEC 菌株已被全球范围内越来越多地视为食源性病原体。在阿根廷，O174 STEC 菌株作为一种新兴病原体而引人注目，是最常见的非 O157 STEC 血清群之一。本研究的目的是对从动物、食品和人类中分离的 41 株 O174：[H21，H28] STEC 菌株进行特征描述。通过stx 基因分型、粘附因子（afaC、eae、iha、lpf、saa 和 toxB）、额外毒素（cdtV、ehxA、subA）和脉冲场凝胶电泳（PFGE）的克隆关系对分离株进行了特征描述。在 30 株 O174:H21 菌株中，最常见的 Stx 亚型是 Stx（56.7%），在 11 株 O174:H28 菌株中，最常见的是 Stx（90.9%）。关于毒力因子，所有菌株均携带 afaC 基因且不携带 eae 和 toxB 基因。在 O174:H21 中，其他因子的频率为 lpf（96.6%）、iha（83.3%）、ehxA 和 saa（10%）和 subA（3.3%），而在 O174:H28 菌株中，iha 和 subA（100%）、lpf（90.9%）、ehxA 和 saa（90.9%）和 cdtV（9.09%）的频率较高。通过 Xbal-PFGE，建立了 29 种模式，相似度为 64.01%，检测到了 3 个聚类。鉴于 O174 血清群是当地的新兴血清群，研究其毒力谱对于了解其潜在的致病性非常重要。
