BioVector® Escherichia coli O157:H7 str. SS52 超级排菌突变研究标准株 / BioVector® Escherichia coli O157:H7 str. SS52 Super-Shedder Research Standard Strain

通用定义

BioVector® Escherichia coli O157:H7 str. SS52 是一种专门用于宿主定殖机理、流行病学传播网络以及肠出血性大肠杆菌（EHEC）致病基因组学研究的人畜共患源“超级排菌”原型标本株（Super-Shedder Isolate）。该菌株最初在美国中西部地区的夏季常规流行病学监测中，从健康携带状态的“超级排菌牛”（Super-shedder cattle）直肠肛门连接处（RAJ）粪便样本中分离获得。其全基因组精细测序已完成并提交至 GenBank，染色体登录号为 CP010304，内源毒力质粒 pO157 登录号为 CP010305。

在食品安全控制与兽医公共卫生学中，SS52 株是一类极具代表性的高环境污染型模型。常规感染牛的排菌量通常仅为 10 到 100 CFU/g，而以 SS52 为代表的超级排菌株在牛体内的排菌浓度可跨越数量级达到 $\ge 10^4 \text{ U/g}$ 以上（该分离株采集记录高达 $6.8 \times 10^5 \text{ CFU/swab}$）。流行病学证据表明，正是这不足 10% 的超级排菌牛释放了环境中超过 90% 的 O157:H7 菌体污染源。这使得 SS52 菌株成为破译细菌如何逃避宿主免疫、建立超强粘附以及导致食品供应链（如牛肉、生菜）大规模污染事件的核心分子遗传学工具。

BioVector® E. coli O157:H7 str. SS52 技术与基因组学参数

1. 核心基因组与特征性多态性（SNPs）

• 染色体基本架构 其染色体全长为 5,488,700 bp 的环状 DNA，包含约 5,632 个开放阅读框（ORFs），整体 G+C 含量约为 50.4%。其在分子进化进化树上高度聚集于更具暴发风险的 Lineage I/II 谱系，与引发严重“菠菜污染事件”的临床大暴发分离株（如 TW14359 和 EC4115）具有极高的亲缘关系。

• 特异性位点与表型连锁 相比于经典的实验室标准致病株 EDL933，SS52 染色体内部富集有 3,106 个独特的单核苷酸多态性（SNPs）。这些突变位点非随机地高度富集于细胞运动性（Motility）、菌毛粘附（Adherence）以及特定碳源代谢（Metabolism）调控通路中。这赋予了 SS52 对牛直肠鳞状上皮细胞具有极强的早期定殖锚定能力。

• 移动遗传元件（MGEs）杂合演变 基因组比较表明，SS52 与其姐妹超级排菌株 SS17（CP008805）在演化后期经历了不同的噬菌体侧向丢失事件。例如，SS52 表现为天然缺失了噬菌体元件 CP-933O，这种动态的移动元件得失直接改变了其表面抗原的暴露程度和生理适应性。

2. 核心毒力因子与抗性配置

• 产 Shiga 毒素基因（STEC 属性） 基因组高度保守携带编码志贺毒素的转化噬菌体溶源区，能够产生高致病性的 Shiga 毒素（Stx）。该毒素是导致人类出血性肠炎以及致死性溶血性尿毒综合征（HUS）的元凶。

• 肠道附着与消除座（LEE 毒力岛） 稳定保留完整的 LEE 毒力岛，包含 eae（内 intimin 粘附素编码基因）、espA、espB 以及 tir 等核心元件，确保细菌能在宿主肠道上皮细胞表面形成特征性的“附着与消除”（Attaching and Effacing, A/E）病理损伤。

• 大毒力质粒 pO157 携带独立的一期环状质粒 pRN52_pO157（94,730 bp），其上集成了周质空间过氧化氢酶（KatP）表达框，为菌体在宿主巨噬细胞吞噬清剿过程中提供了极强的抗氧化防御保护。

• 天然抗性背景 基因组染色体背景中整合有广泛存在的巨噬细胞/大环内酯类外排泵基因 mdf(A)，对基础的某些抗生素表现出天然的低敏感性背景。

主要科研应用

1. 兽医公共卫生与“超级排菌”干预阻断机制

• 黏膜定殖阻断剂评价 利用 SS52 的强粘附表型，在体外牛直肠外体模型或上皮细胞系上，筛选旨在竞争性阻断 E. coli O157 锚定的新型益生菌抗体、寡糖寡肽拦截剂或饲料添加剂。

2. 诊断试剂盒与基因芯片多态性特异性校准

• 高通量测序（NGS）质控 作为包含多点高频 SNPs 突变的阳性质控株，用于临床多重 PCR 检测试剂盒以及微阵列芯片的灵敏度边界评估，防止因基因漂变导致超级传播株在物流链监测中发生“假阴性”漏检。

技术指标简表

⚠️ 临床敏感提示：

根据临床微生物学指南，在涉及 suspected EHEC/STEC（如 SS52 菌株）的研究中，抗生素的滥用被严格列为反指征（Contraindicated）。在诱导环境下使用某些促裂解类抗生素会剧烈激活细菌体内的原噬菌体进入裂解周期，导致大量的志贺毒素（Shiga Toxin）瞬间释放。这在人畜共患毒性评价实验中会导致宿主细胞内皮损伤加速，极易诱发微血管病性溶血性贫血和急性肾衰竭（HUS）。

BioVector® Escherichia coli O157:H7 str. SS52 Super-Shedder Research Standard Strain

General Definition

BioVector® Escherichia coli O157:H7 str. SS52 is a zoonotic super-shedder prototype isolate developed for investigating host colonization kinetics, epidemiological transmission dynamics, and enterohemorrhagic E. coli (EHEC) pathogenic genomics. This particular strain was discovered during routine regional surveillance in the United States and was isolated directly from the terminal recto-anal junction (RAJ) of an asymptomatic "super-shedder" bovine host. Its complete sequence has been deposited in GenBank under accession numbers CP010304 (chromosome) and CP010305 (large virulence plasmid pO157).

In food safety optimization and veterinary public health infrastructure, the SS52 strain represents a highly critical model for environmental contamination. While typical colonized cattle excrete this pathogen at low ranges of 10 to 100 CFU/g of feces, super-shedder individuals carrying strains like SS52 excrete the bacteria at magnitudes $\ge 10^4 \text{ CFU/g}$ (with this specific isolate recorded at $6.8 \times 10^5 \text{ CFU/rectal swab}$). Epidemiological assessments confirm that this minor subpopulation (<10% of cattle) is responsible for over 90% of the total environmental O157:H7 load. Consequently, SS52 serves as a pivotal genomic reference to decipher enhanced mucosal adherence, survival under host immune duress, and mechanisms driving widespread food supply contamination outbreaks.

BioVector® E. coli O157:H7 str. SS52 Technical & Genomic Specifications

1. Core Genome and Specific Polymorphisms (SNPs)

• Chromosomal Architecture Features a circular DNA chromosome spanning 5,488,700 bp containing approximately 5,632 open reading frames (ORFs) with a stable G+C content of 50.4%.Phylogenetically, it maps closely to Lineage I/II, placing it in proximity to clinical outbreak strains such as TW14359 and EC4115 associated with severe leafy vegetable contamination events.

• SNP-Phenotype Linkage Compared to the classic standard pathogenic reference EDL933, the SS52 genome contains 3,106 unique single nucleotide polymorphisms (SNPs). These genetic variations are heavily concentrated within functional clusters governing bacterial motility, fimbrial adherence, and specialized carbohydrate utilization pathways, explaining its high binding affinity toward bovine rectal epithelial cells.

• Mobile Genetic Element (MGE) Dynamics Comparative alignments demonstrate distinct horizontal gene transfer events between SS52 and sister super-shedder isolates like SS17. For instance, SS52 is characterized by the natural absence of the prophage element CP-933O, showcasing ongoing structural evolution affecting surface antigen presentation.

2. Virulence Factor Configurations & Resistome

• Shiga Toxin Production (STEC Profile) Integrates the essential prophage regions encoding Shiga toxins (Stx), which inhibit eukaryotic protein synthesis and cause hemorrhagic colitis and potentially fatal Hemolytic Uremic Syndrome (HUS) in humans.

• Locus of Enterocyte Effacement (LEE Island) Retains a fully functional LEE pathogenicity island including the eae gene (encoding the adherence factor intimin) along with espA, espB, and tir, ensuring the capability to induce classic attaching and effacing (A/E) microvilli lesions.

• Virulence Episome pO157 Features the autonomous plasmid pRN52_pO157 (94,730 bp), which carries the periplasmic catalase-peroxidase gene (katP), providing robust oxidative stress protection against host macrophage engulfment.

• Intrinsic Resistome Possesses the widely distributed multidrug efflux pump gene mdf(A), conferring a baseline resistance profile against specific macrolides under standard metabolic conditions.

Primary Research Applications

1. Veterinary Interventions and Shedding Mitigation

• Colonization Inhibitor Screening Utilizing the highly adherent phenotype of SS52 on bovine mucosal models to evaluate competitive exclusion agents, prebiotic oligosaccharides, or custom targeted feed additives designed to displace O157 colonization at the RAJ site.

2. Diagnostic Assay and Next-Generation Sequencing Validation

• Assay Sensitivity Control Serves as an excellent genomic validation control strain for multiplex PCR diagnostics and microarrays to ensure target design robustness against natural SNP variations, eliminating false negatives during routine supply chain screenings.

Technical Data Summary

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