Infection mechanism of E.coli 0157 to native human colon epithelial cells

本课题旨在阐明肠出血性大肠杆菌的感染机制。coli O157对人肠上皮细胞的体外培养，建立了原代培养人结肠上皮细胞的方法。大肠杆菌O157已经显示出侵入天然结肠上皮细胞的程度与肠道沙门氏菌相当，这通过庆大霉素杀死细胞外细菌来证明。3）共聚焦荧光显微镜和电子显微镜观察证实了胞内细菌的存在，庆大霉素保护试验也证实了E. coliO 157表达上皮细胞标记而不表达单核细胞标记。coli 0157和SaleA对大肠杆菌的侵袭能力相似，而SaleA对大肠杆菌的侵袭能力较低。6）利用细菌缺失位点的等基因缺失突变体，证实了sepL是大肠杆菌侵袭能力所必需的，而eaeA、espA和Tir则不是必需的。

The purpose of this project is to elucidate the infection mechanism of enterohemorrhagic E. coli O157 to human intestinal epithelial cells.1) The primary culture of native epithelial cells from human colon has been established.2) E. coli O157 has been shown to invade the native colon epithelial cells to a comparable extent with Salmonella enterica as proved by killing the extracellular bacteria by gentamicin. The invasion was dependent on the action of cytoskeletons and cell surface cholesterol content.3) The morphological insights using con focal fluorescent microscopy and electromicroscopy confirmed the intracellular bacteria, in addition to gentamicin protection assay.4) The target cells of E. coli O157 were shown to express epithelial markers but not monocyte markers.5) When another type of epithelial cell, Hela was tested for the infection of E. coli 0157 and salmonella, the latter invaded to a similar degree of colon cells but not the former.6) Employing the isogenic deletion mutants of bacterial effacement locus, the sepL was proved to be essential for the invasion activity, whereas not was eaeA, espA or Tir.