Department of Microbiology, Pathology North-Hunter, NSW Health Pathology, John Hunter Hospital, Locked Bag 1, HRMC, Australia; Australian Rickettsial Reference Laboratory, Barwon Health, Geelong, Australia.
Am J Trop Med Hyg. 2013 Oct;89(4):800-3. doi: 10.4269/ajtmh.12-0653. Epub 2013 Aug 19.
The Nine Mile phase II clone 4 (NMIIC4) strain of Coxiella burnetii is an attenuated phase II strain that has lost the genes for virulence determinant type 1 lipopolysaccharide. These bacteria were very virulent for severe combined immunodeficient (SCID) mice. The lethal dose 50 (LD50) was ~10 bacteria. Infected SCID mice died between Day 28 and Day 53 post-infection. At termination of the experiment (Day 60) only 5 of 24 mice had survived. The degree of splenomegaly was directly related to the bacterial load in the SCID mice spleens. The NMIIC4 was avirulent in immunocompetent wild mice and bacterial DNA copies in splenic tissue were extremely low. The SCID mice that were inoculated with high doses of heat inactivated NMIIC4 C. burnetii were all alive at Day 60 and without splenomegaly. It appears that the phase I lipopolysaccharide present in virulent Nine Mile phase I but not in attenuated NMIIC4 is not the only virulence factor for C. burnetii.
贝氏柯克斯体九英里二期克隆 4（NMIIC4）株是一种减毒的二期菌株，它失去了毒力决定因素 1 型脂多糖的基因。这些细菌对严重联合免疫缺陷（SCID）小鼠具有很强的毒性。半数致死量（LD50）约为 10 个细菌。感染的 SCID 小鼠在感染后第 28 天至第 53 天之间死亡。在实验结束时（第 60 天），24 只小鼠中只有 5 只存活。脾肿大的程度与 SCID 小鼠脾脏中的细菌负荷直接相关。NMIIC4 在免疫功能正常的野生小鼠中无致病性，且脾脏组织中的细菌 DNA 拷贝极低。接种高剂量热灭活 NMIIC4 贝氏柯克斯体的 SCID 小鼠在第 60 天都存活且无脾肿大。似乎存在于毒力九英里一期而非减毒 NMIIC4 中的一期脂多糖并非贝氏柯克斯体的唯一毒力因子。
