ObjectivesTo study the mechanism of brain damage caused byStaphylococcus epidermidis (SE) in mice. Methods A total of 80 neonatal mice of postnatal day 1 (PND1) were divided into SE group (48 mice), normal saline (NS) group (16 mice) and control group (16 mice). Mice in SE group were intravenously injected with 50 μl SE (108/ml). Mice in NS group were given 50 μl NS. Mice in control group were not intervened. At different time points after SE injection (6 h, 24 h, 72 h, 5 d, 7 d), the CFU of brain, blood, and spleen were calculated. Serial sections of parafifn-embedded brain tissue were used for detection of ionized calcium-binding adaptor moleculor1 (Iba-1) by immunohistochemical staining. The positive cells were calculated. ELISA was used to measure the levels of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-5 (IL-5), interleukin-6 (IL-6) of brain at 6 h and 24 h after SE injection.Results There was no SE in brain in different time points. The CFU was at the highest level at 6 h and then decreased after 24 h in blood and spleen. The Iba-1 positive cells in SE group were signiifcantly increased compared to NS group and control group at 24 h and 72 h (P<0.05). There was no difference of Iba-1 positive cells be-tween 24 h and 72 h after SE injection (P>0.05). The levels of TNF-α, IL-1β, IL-5, and IL-6 were signiifcantly higher in SE group than those in NS and control at 6 h and 24 h (P<0.05). The levels of TNF-α, IL-1β, IL-5, and IL-6 were signiifcantly lower in SE group at 24 h than those in SE group at 6 h (P<0.01).Conclusions It is suggested that cytokines produced by microglias may be the mediators of SE-caused brain damage.%目的：探讨表皮葡萄球菌(SE)感染引起新生小鼠脑损伤的机制。方法出生第1天新生小鼠共80只，分为SE组、生理盐水(NS)组、对照组，其中SE组48只，NS组及对照组各16只。SE组静脉注射108/ml的SE 50μl，NS组给予等量的NS，对照组不予任何处理。在注射后不同时间点(6 h、24 h、72 h、5 d、7 d)取血、脾、脑过夜培养后做细菌菌落(CFU)计数；在24 h和72 h取脑组织石蜡包埋后连续切片，用于离子钙接头蛋白抗体(Iba-1)免疫组化染色；在6 h和24 h取脑组织用酶联免疫吸附试验测定肿瘤坏死因子(TNF-α)、白介素-1β(IL-1β)、IL-5、IL-6。结果注射后不同时间点，SE组小鼠脑组织中均未发现细菌，血和脾中6 h菌落计数最高，24 h后迅速下降。在注射后24 h、72 h，SE组、NS组和对照组三组之间大脑中Iba-1阳性细胞数的差异有统计学意义(H=75.56、69.54，P均<0.001)；其中SE组高于NS组和对照组，差异有统计学意义(P均<0.05)。各组在24 h与72 h两个时间点，大脑中Iba-1阳性细胞数差异无统计学意义(P均>0.05)。在注射后6 h、24 h，三组之间大脑TNF-α、IL-1β、IL-5和IL-6水平差异有统计学意义(H=59.07~319.34，P均<0.001)；其中SE组大脑中各细胞因子含量均高于NS组和对照组，差异有统计学意义(P<0.05)。SE组在注射后24 h，与6 h时相比，TNF-α、IL-1β、IL-5和IL-6水平均有下降，两时间点差异均有统计学意义(P<0.01)。结论SE引起的新生小鼠的脑损伤可能通过激活脑内小胶质细胞，同时分泌大量的细胞因子而引起。
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