Aga Khan University, Stadium Road, Karachi, Pakistan.
Exp Parasitol. 2011 Aug;128(4):409-13. doi: 10.1016/j.exppara.2011.05.008. Epub 2011 May 15.
The type III secretion system among Gram-negative bacteria is known to deliver effectors into host cell to interfere with host cellular processes. The type III secretion system in Yersina, Pseudomonas and Enterohemorrhagic Escherichia coli have been well documented to be involved in the bacterial pathogenicity. The existence of type III secretion system has been demonstrated in neuropathogenic E. coli K1 strains. Here, it is observed that the deletion mutant of type III secretion system in E. coli strain EC10 exhibited defects in the invasion and intracellular survival in Acanthamoeba castellanii (a keratitis isolate) compared to its parent strain. Next, it was determined whether type III secretion system plays a role in E. coli K1 survival inside Acanthamoeba during the encystment process. Using encystment assays, our findings revealed that the type III secretion system-deletion mutant exhibited significantly reduced survival inside Acanthamoeba cysts compared with its parent strain, EC10 (P<0.01). This is the first demonstration that the type III secretion system plays an important role in E. coli interactions with Acanthamoeba. A complete understanding of how amoebae harbor bacterial pathogens will help design strategies against E. coli transmission to the susceptible hosts.
革兰氏阴性菌的 III 型分泌系统被认为能将效应蛋白输送到宿主细胞内，从而干扰宿主细胞的过程。肠杆菌、假单胞菌和肠出血性大肠杆菌的 III 型分泌系统已被证明与细菌的致病性有关。神经致病性大肠杆菌 K1 株中存在 III 型分泌系统。在这里，观察到大肠杆菌菌株 EC10 的 III 型分泌系统缺失突变体在棘阿米巴（角膜炎分离株）中的入侵和细胞内存活方面存在缺陷，与亲本菌株相比。接下来，确定 III 型分泌系统是否在大肠杆菌 K1 包囊过程中在棘阿米巴体内的存活中发挥作用。通过包囊试验，我们的发现表明，III 型分泌系统缺失突变体在棘阿米巴包囊内的存活明显低于亲本菌株 EC10（P<0.01）。这是首次证明 III 型分泌系统在大肠杆菌与棘阿米巴的相互作用中发挥重要作用。全面了解阿米巴如何携带细菌病原体将有助于设计针对大肠杆菌向易感宿主传播的策略。
