中文摘要：

大肠杆菌是导致新生儿细菌性脑膜炎最常见的革兰氏阴性致病菌．为探讨毒力岛基因ibeT在大肠杆菌K1株致病过程中的作用，构建了ibeT基因缺失的大肠杆菌K1株，细菌在细胞内存活试验结果显示，ibeT基因缺失抑制了大肠杆菌K1株在人脑微血管内皮细胞中的生长．利用激光共聚焦扫描显微镜观察到，在细菌侵袭进入人脑微血管内皮细胞后，与野生型相比，ibeT基因缺失突变株较多地滞留在溶酶体内；透射电镜结果进一步显示，ibeT基因缺失使大肠杆菌K1株逃逸ECV（含有大肠杆菌的囊泡）的能力发生了下降，继而使其在细胞浆内的复制减少．利用体外模拟的弱酸性环境，检测大肠杆菌菌体胞内的缓冲容量，发现ibeT基因缺失突变株菌体胞内的缓冲能力较野生型低．这些结果提示，在大肠杆菌K1株侵袭进入人脑微血管内皮细胞后，ibeT基因有利于大肠杆菌降解ECV膜，避免与溶酶体融合，进而促使大肠杆菌逃逸进入细胞浆并进行复制．

英文摘要：

Escherichia coli is the most common gram-negative organism causing neonatal meningitis. In order to characterize the role of the pathogenicity island gene ibeT of Escherichia coli K1 in the pathogenesis of neonatal meningitis, an ibeT gene isogenic in-frame deletion mutant strain was constructed. Intracellular survival assay in human brain microvascular endothelial cells （HBMECs） showed that the deletion of ibeT inhibited the growth of Escherichia coli K1 within HBMECs. Confocal microscopy analysis showed that much more ibeT mutant remained in lysosomes of HBMECs compared with wild type Escherichia coli K1 after bacterial invasion into HBMECs. Transmission electron micrographs further showed that ibeT mutant strain was failed to disrupt the Escherichia coli containing vacuole （ECV） and escape into the cytoplasm. Furthermore, cytoplasmic buffering capacities of ibeT mutant were lower than wild type Escherichia coli K1 at pH 6.5 and pH 6.0. These results suggested that the expression of ibeT in Escherichia coli K1 contributed to ECV membrane degradation and subsequent escape from lysosomes into the cytoplasm for replication after Escherichia coli K1 invasion into HBMECs.