Stephan Roger, Zhang Wenlan, Bielaszewska Martina, Mellmann Alexander, Karch Helge
Institute for Food Safety and Hygiene, University of Zurich, Switzerland.
Foodborne Pathog Dis. 2009 Mar;6(2):235-43. doi: 10.1089/fpd.2008.0205.
Enterohemorrhagic E. coli (EHEC) O157:H7/H(-) (nonmotile) exist as Shiga toxin gene (stx)-positive and stx-negative variants in patients and the environment. We analyzed molecular characteristics, phenotypes, and the phylogenetic background of three stx-negative E. coli O157:H7/H(-) strains isolated from cattle and a pig and compared them with those of human EHEC and stx-negative E. coli O157:H7/H(-). All three animal strains contained fliCH7 and two contained eae. One eae-positive strain (O157:H(-)) was sorbitol-fermenting (SF) and the other (O157:H7) was non-sorbitol-fermenting (nSF). These two strains shared a spectrum of non-stx putative virulence and fitness genes with human nSF and SF EHEC and stx-negative E. coli O157:H7/H(-) and belonged, similar to the vast majority of human isolates, to sequence type (ST) 11 in multilocus sequence typing. In contrast, the eae-negative O157:H7 animal isolate, which was SF, differed in spectrum of virulence genes and also differed phylogenetically (ST717) from the two eae-positive strains and the human EHEC and stx-negative E. coli O157:H7/H(-). In contrast to efforts with human stx-negative E. coli O157:H(-), attempts to transduce the two stx-negative/eae-positive animal O157:H7/H(-) strains with stx(2)-encoding phages from human SF and nSF EHEC O157:H7/H(-) failed, despite the animal strains having intact loci where such phages integrate in human EHEC O157 (wrbA and yecE). The role of animal stx-negative/eae-positive and stx-negative/eae-negative E. coli O157:H7/H(-) in their natural source and in human infections needs further investigation.
肠出血性大肠杆菌（EHEC）O157:H7/H(-)（无动力）在患者和环境中以志贺毒素基因（stx）阳性和stx阴性变体形式存在。我们分析了从牛和猪中分离出的三株stx阴性大肠杆菌O157:H7/H(-)菌株的分子特征、表型和系统发育背景，并将它们与人类EHEC和stx阴性大肠杆菌O157:H7/H(-)的特征进行了比较。所有三株动物菌株都含有fliCH7，其中两株含有eae。一株eae阳性菌株（O157:H(-)）能发酵山梨醇（SF），另一株（O157:H7）不能发酵山梨醇（nSF）。这两株菌株与人类nSF和SF EHEC以及stx阴性大肠杆菌O157:H7/H(-)共享一系列非stx假定毒力和适应性基因，并且与绝大多数人类分离株一样，在多位点序列分型中属于序列型（ST）11。相比之下，eae阴性的O157:H7动物分离株能发酵山梨醇，其毒力基因谱不同，并且在系统发育上（ST717）与两株eae阳性菌株以及人类EHEC和stx阴性大肠杆菌O157:H7/H(-)也不同。与对人类stx阴性大肠杆菌O157:H(-)的研究不同，尽管动物菌株具有噬菌体在人类EHEC O157中整合的完整位点（wrbA和yecE），但尝试用来自人类SF和nSF EHEC O157:H7/H(-)的携带stx(2)的噬菌体转导两株stx阴性/eae阳性动物O157:H7/H(-)菌株的实验失败了。动物stx阴性/eae阳性和stx阴性/eae阴性大肠杆菌O157:H7/H(-)在其自然宿主以及人类感染中的作用需要进一步研究。
