Delannoy Sabine, Chaves Byron D, Ison Sarah A, Webb Hattie E, Beutin Lothar, Delaval José, Billet Isabelle, Fach Patrick
Food Safety Laboratory, Université Paris-Est, Anses (French Agency for Food, Environmental and Occupational Health and Safety), Platform IdentyPath Maisons-Alfort, France.
Department of Animal and Food Sciences, Texas Tech University Lubbock, TX, USA.
Front Microbiol. 2016 Jan 22;7:1. doi: 10.3389/fmicb.2016.00001. eCollection 2016.
Current methods for screening Enterohemorrhagic Escherichia coli (EHEC) O157 and non-O157 in beef enrichments typically rely on the molecular detection of stx, eae, and serogroup-specific wzx or wzy gene fragments. As these genetic markers can also be found in some non-EHEC strains, a number of "false positive" results are obtained. Here, we explore the suitability of five novel molecular markers, espK, espV, ureD, Z2098, and CRISPRO26:H11 as candidates for a more accurate screening of EHEC strains of greater clinical significance in industrialized countries. Of the 1739 beef enrichments tested, 180 were positive for both stx and eae genes. Ninety (50%) of these tested negative for espK, espV, ureD, and Z2098, but 12 out of these negative samples were positive for the CRISPRO26:H11 gene marker specific for a newly emerging virulent EHEC O26:H11 French clone. We show that screening for stx, eae, espK, and espV, in association with the CRISPRO26:H11 marker is a better approach to narrow down the EHEC screening step in beef enrichments. The number of potentially positive samples was reduced by 48.88% by means of this alternative strategy compared to the European and American reference methods, thus substantially improving the discriminatory power of EHEC screening systems. This approach is in line with the EFSA (European Food Safety Authority) opinion on pathogenic STEC published in 2013.
目前用于筛查牛肉增菌液中肠出血性大肠杆菌（EHEC）O157和非O157的方法通常依赖于对stx、eae以及血清群特异性wzx或wzy基因片段的分子检测。由于这些基因标记在一些非EHEC菌株中也能找到，所以会获得一些“假阳性”结果。在此，我们探究了五个新型分子标记espK、espV、ureD、Z2098和CRISPRO26:H11作为更准确筛查工业化国家中具有更高临床意义的EHEC菌株候选标记的适用性。在检测的1739份牛肉增菌液中，180份stx和eae基因均呈阳性。其中90份（50%）对espK、espV、ureD和Z2098检测呈阴性，但这些阴性样本中有12份对新出现的毒力型EHEC O26:H11法国克隆特异性的CRISPRO26:H11基因标记呈阳性。我们表明，联合CRISPRO26:H11标记对stx、eae、espK和espV进行筛查是缩小牛肉增菌液中EHEC筛查步骤的更好方法。与欧美参考方法相比，通过这种替代策略，潜在阳性样本数量减少了48.88%，从而显著提高了EHEC筛查系统的鉴别能力。该方法与欧洲食品安全局（EFSA）2013年发布的关于致病性产志贺毒素大肠杆菌（STEC）的意见一致。
