Shiga toxin-producing Escherichia coli (STEC) in sprouts have caused large scale outbreaks in the past involving severe illness. The combination of this very diverse pathogen and a food matrix with high numbers of background microbiota poses a particular challenge for detection and isolation. An acid treatment of the enrichment before plating on agar has been shown to improve the recovery of STEC from sprouts. After enrichment in buffered peptone water (BPW) at 37 °C we applied an acid treatment, followed by plating on tryptone bile x-glucuronide (TBX) agar (acid bile method). An inter-laboratory study was organized with 21 laboratories taking part to evaluate the performance parameters and applicability of the acid bile method. A sample set of six sprout samples was prepared consisting of two uninoculated samples and four spiked samples, each containing one of two STEC strains at one of two concentrations (low and high). Analyzing a set of six samples at the National Reference Laboratory (NRL E. coli), we determined the relative abundance of STEC without, after acid-, after bile- and after acid-bile treatment using real-time PCR. The participating laboratories successfully applied the acid bile method and were better able to detect (sensitivity 92.9% vs. 70.0%) and isolate (sensitivity 87.5% vs. 31.3%) STEC from positive samples using the acid bile method compared to non-acid methods. The relative limit of detection (RLOD) after isolation using the acid bile method (vs. non-acid method) was <1 for both STEC strains used, BfR-EC-14434 O133:H25 (0.146) and BfR-EC-16015 O26:H11 (0.073). A collection of STEC (n = 71) of diverse type and characteristics was assessed for their resistance towards the acid bile treatment selection. The majority (n = 65) of STEC strains could be recovered after acid treatment on TBX plates. However, a few strains (n = 6), among them clinical isolates were (partly) sensitive. These results suggest that an acid bile method is a rapid and reasonable approach to improve the recovery of STEC from sprouts when used in combination with methods targeting other selection markers.

中文翻译：

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利用盐酸和胆汁抗性，优化检测和从豆芽中分离出产生志贺毒素的大肠杆菌（STEC）。

过去，产生志贺毒素的大肠杆菌（STEC）已引起大规模暴发，涉及重病。这种非常多样的病原体与具有大量背景微生物的食物基质的结合对检测和分离提出了特殊的挑战。已显示在平板上琼脂上进行酸富集处理可以提高STEC从新芽中的回收率。在37°C的缓冲蛋白ept水（BPW）中富集后，我们进行了酸处理，然后在胰蛋白bi胆汁x-葡萄糖醛酸（TBX）琼脂上平板接种（胆汁胆汁法）。与21个实验室一起组织了实验室间研究，以评估酸胆方法的性能参数和适用性。制备了一套包含六个未处理样品的样品，其中包括两个未接种样品和四个加标样品，每个都包含两种浓度（低和高）之一的两个STEC菌株之一。在国家参考实验室（NRL E. coli）上分析了一组六个样品，我们确定了使用实时PCR进行酸，胆汁和酸胆处理后，STEC的相对丰度。参与的实验室成功应用了酸胆方法，与非酸方法相比，使用酸胆方法能够更好地从阳性样品中检测（灵敏度为92.9％vs. 70.0％）和分离（灵敏度为87.5％vs. 31.3％）。 。对于两个使用的STEC菌株，BfR-EC-14434 O133：H25（0.146）和BfR-EC-16015 O26，使用酸胆汁方法（相对于非酸方法）分离后的相对检出限（RLOD）<1 ：H11（0.073）。评估了不同类型和特征的STEC集合（n = 71）对酸性胆汁治疗选择的抵抗力。在TBX板上进行酸处理后，可以回收到大多数（n = 65）STEC菌株。然而，少数菌株（n = 6），其中临床分离株是（部分）敏感的。这些结果表明，与针对其他选择标记的方法结合使用时，胆汁酸方法是提高芽中STEC回收率的一种快速而合理的方法。