Söderlund Robert, Flink Catarina, Aspán Anna, Eriksson Erik
Department of Microbiology, Swedish National Veterinary Institute (SVA), Uppsala, Sweden.
Department of Biology, Swedish Food Agency, Uppsala, Sweden.
Access Microbiol. 2023 May 3;5(5). doi: 10.1099/acmi.0.000577.v3. eCollection 2023.
Wheat flour has been identified as the source of multiple outbreaks of gastrointestinal disease caused by shiga toxin-producing (STEC). We have investigated the presence and genomic characteristics of STEC and related atypical enteropathogenic (aEPEC) in 200 bags of Swedish-produced retail wheat flour, representing 87 products and 25 brands. Samples were enriched in modified tryptone soya broth (mTSB) and screened with real-time PCR targeting , and , and the serogroups O157, O121 and O26. Isolation was performed by immunomagnetic separation (IMS) for suspected STEC/aEPEC O157, O121 and O26, and by screening pools of colonies for other STEC. Real-time PCR after enrichment revealed 12 % of samples to be positive for shiga toxin genes ( and/or ) and 11 % to be positive for intimin (). Organic production, small-scale production or whole grain did not significantly influence shiga toxin gene presence or absence in a generalized linear mixed model analysis. Eight isolates of STEC were recovered, all of which were intimin-negative. Multiple serotype/sequence type/shiga toxin subtype combinations that have also been found in flour samples in other European countries were recovered. Most STEC types recovered were associated with sporadic cases of STEC among humans in Sweden, but no types known to have caused outbreaks or severe cases of disease (i.e. haemolytic uraemic syndrome) were found. The most common finding was O187:H28 ST200 with , with possible links to cervid hosts. Wildlife associated with crop damage is a plausible explanation for at least some of the surprisingly high frequency of STEC in wheat flour.
小麦粉已被确定为产志贺毒素大肠杆菌（STEC）引起的多起胃肠道疾病暴发的源头。我们调查了200袋瑞典产零售小麦粉中STEC及相关非典型肠致病性大肠杆菌（aEPEC）的存在情况和基因组特征，这些小麦粉代表了87种产品和25个品牌。样本在改良胰蛋白胨大豆肉汤（mTSB）中增菌，并用针对、和以及血清型O157、O121和O26的实时PCR进行筛查。通过免疫磁珠分离（IMS）对疑似STEC/aEPEC O157、O121和O26进行分离，并通过筛查菌落池来检测其他STEC。增菌后的实时PCR显示，12%的样本志贺毒素基因（和/或）呈阳性，11%的样本intimin（）呈阳性。在广义线性混合模型分析中，有机生产、小规模生产或全谷物对志贺毒素基因的存在与否没有显著影响。共分离出8株STEC，均为intimin阴性。还发现了在其他欧洲国家的面粉样本中也存在的多种血清型/序列型/志贺毒素亚型组合。分离出的大多数STEC类型与瑞典人类中STEC的散发病例有关，但未发现已知会导致疾病暴发或严重病例（即溶血尿毒综合征）的类型。最常见的是O187:H28 ST200，带有，可能与鹿宿主有关。与作物损害相关的野生动物是小麦粉中STEC出现频率高得出奇的至少部分原因的一个合理解释。
