Li Mo-fei, Sun Li, Li Jun
Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China; Graduate University of the Chinese Academy of Sciences, Beijing 100049, China.
Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China.
Fish Shellfish Immunol. 2015 Apr;43(2):325-9. doi: 10.1016/j.fsi.2014.12.037. Epub 2015 Jan 6.
Edwardsiella tarda is a Gram-negative bacterium with a broad host range that includes a wide variety of farmed fish as well as humans. E. tarda has long been known to be able to survive in host serum, but the relevant mechanism is unclear. In this study, we investigated the fundamental question, i.e. whether E. tarda activated serum complement or not. We found that (i) when incubated with flounder serum, E. tarda exhibited a high survival rate (87.6%), which was slightly but significantly reduced in the presence of Mg(2+); (ii) E. tarda-incubated serum possessed strong hemolytic activity and bactericidal activity, (iii) compared to the serum incubated with a complement-sensitive laboratory Escherichia coli strain, E. tarda-incubated serum exhibited much less chemotactic activity, (iv) in contrast to the serum incubated with live E. tarda, the serum incubated with heat-inactivated E. tarda exhibited no apparent hemolytic capacity. Taken together, these results indicate for the first time that E. tarda circumvents serum attack by preventing, to a large extent, complement activation via the alternative pathway, and that heat-labile surface structures likely play an essential role in the complement evasion of E. tarda.
迟缓爱德华氏菌是一种革兰氏阴性菌，宿主范围广泛，包括多种养殖鱼类以及人类。长期以来已知迟缓爱德华氏菌能够在宿主血清中存活，但相关机制尚不清楚。在本研究中，我们调查了一个基本问题，即迟缓爱德华氏菌是否激活血清补体。我们发现：（i）与比目鱼血清一起孵育时，迟缓爱德华氏菌表现出较高的存活率（87.6%），在存在Mg(2+)的情况下存活率略有但显著降低；（ii）与迟缓爱德华氏菌孵育的血清具有很强的溶血活性和杀菌活性；（iii）与用对补体敏感的实验室大肠杆菌菌株孵育的血清相比，与迟缓爱德华氏菌孵育的血清表现出低得多的趋化活性；（iv）与用活的迟缓爱德华氏菌孵育的血清相反，用热灭活的迟缓爱德华氏菌孵育的血清没有明显的溶血能力。综上所述，这些结果首次表明，迟缓爱德华氏菌通过在很大程度上阻止补体通过替代途径激活来规避血清攻击，并且热不稳定表面结构可能在迟缓爱德华氏菌逃避补体方面发挥重要作用。
