Hatcher Brandon L, Hale Joanetha Y, Briles David E
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
Infect Immun. 2016 Aug 19;84(9):2607-15. doi: 10.1128/IAI.01514-15. Print 2016 Sep.
Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and neurological sequelae in children worldwide. Acute bacterial meningitis is widely considered to result from bacteremia that leads to blood-brain barrier breakdown and bacterial dissemination throughout the central nervous system (CNS). Previously, we showed that pneumococci can gain access to the CNS through a nonhematogenous route without peripheral blood infection. This access is thought to occur when the pneumococci in the upper sinus follow the olfactory nerves and enter the CNS through the olfactory bulbs. In this study, we determined whether the addition of exogenous sialic acid postcolonization promotes nonhematogenous invasion of the CNS. Previously, others showed that treatment with exogenous sialic acid post-pneumococcal infection increased the numbers of CFU recovered from an intranasal mouse model of infection. Using a pneumococcal colonization model, an in vivo imaging system, and a multiplex assay for cytokine expression, we demonstrated that sialic acid can increase the number of pneumococci recovered from the olfactory bulbs and brains of infected animals. We also show that pneumococci primarily localize to the olfactory bulb, leading to increased expression levels of proinflammatory cytokines and chemokines. These findings provide evidence that sialic acid can enhance the ability of pneumococci to disseminate into the CNS and provide details about the environment needed to establish nonhematogenous pneumococcal meningitis.
肺炎链球菌是全球儿童细菌性脑膜炎和神经后遗症的主要病因。急性细菌性脑膜炎被广泛认为是由菌血症导致血脑屏障破坏和细菌在整个中枢神经系统(CNS)播散所致。此前,我们发现肺炎链球菌可通过非血源性途径进入中枢神经系统,而无需外周血感染。这种进入被认为是当上颌窦中的肺炎链球菌沿着嗅神经并通过嗅球进入中枢神经系统时发生的。在本研究中,我们确定定植后添加外源性唾液酸是否会促进中枢神经系统的非血源性侵袭。此前,其他人表明在肺炎链球菌感染后用外源性唾液酸治疗可增加从鼻内感染小鼠模型中回收的菌落形成单位(CFU)数量。使用肺炎链球菌定植模型、体内成像系统和细胞因子表达多重检测方法,我们证明唾液酸可增加从感染动物的嗅球和大脑中回收的肺炎链球菌数量。我们还表明,肺炎链球菌主要定位于嗅球,导致促炎细胞因子和趋化因子的表达水平增加。这些发现提供了证据,表明唾液酸可增强肺炎链球菌扩散到中枢神经系统的能力,并提供了建立非血源性肺炎链球菌脑膜炎所需环境的详细信息。