Department of Pediatrics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Department of Pathology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Microbiology (Reading). 2009 Dec;155(Pt 12):4135-4144. doi: 10.1099/mic.0.033175-0. Epub 2009 Sep 17.
Otitis media (OM) is one of the most frequent diseases in childhood, and Streptococcus pneumoniae is among the main causative bacterial agents. Since current experimental models used to study the bacterial pathogenesis of OM have several limitations, such as the invasiveness of the experimental procedures, we developed a non-invasive murine OM model. In our model, adapted from a previously developed rat OM model, a pressure cabin is used in which a 40 kPa pressure increase is applied to translocate pneumococci from the nasopharyngeal cavity into both mouse middle ears. Wild-type pneumococci were found to persist in the middle ear cavity for 144 h after infection, with a maximum bacterial load at 96 h. Inflammation was confirmed at 96 and 144 h post-infection by IL-1beta and TNF-alpha cytokine analysis and histopathology. Subsequently, we investigated the contribution of two surface-associated pneumococcal proteins, the streptococcal lipoprotein rotamase A (SlrA) and the putative proteinase maturation protein A (PpmA), to experimental OM in our model. Pneumococci lacking the slrA gene, but not those lacking the ppmA gene, were significantly reduced in virulence in the OM model. Importantly, pneumococci lacking both genes were significantly more attenuated than the DeltaslrA single mutant. This additive effect suggests that SlrA and PpmA exert complementary functions during experimental OM. In conclusion, we have developed a highly reproducible and non-invasive murine infection model for pneumococcal OM using a pressure cabin, which is very suitable to study pneumococcal pathogenesis and virulence in vivo.
中耳炎（OM）是儿童中最常见的疾病之一，肺炎链球菌是主要的致病细菌之一。由于目前用于研究 OM 细菌发病机制的实验模型存在许多局限性，例如实验程序的侵袭性，因此我们开发了一种非侵入性的小鼠 OM 模型。在我们的模型中，从先前开发的大鼠 OM 模型中进行了改编，使用了一个压力舱，在压力舱中将 40 kPa 的压力增加用于将肺炎链球菌从鼻咽腔转移到两只小鼠的中耳。感染后，野生型肺炎链球菌在中耳腔中持续存在 144 小时，最大细菌负荷在 96 小时。在感染后 96 和 144 小时，通过 IL-1beta 和 TNF-alpha 细胞因子分析和组织病理学证实了炎症。随后，我们在我们的模型中研究了两种表面相关的肺炎链球菌蛋白，链球菌脂蛋白旋转酶 A（SlrA）和假定的蛋白酶成熟蛋白 A（PpmA）对实验性 OM 的贡献。缺乏 slrA 基因的肺炎链球菌，而不是缺乏 ppmA 基因的肺炎链球菌，在 OM 模型中的毒力明显降低。重要的是，缺乏这两个基因的肺炎链球菌比 DeltaslrA 单突变体明显更衰减。这种累加效应表明 SlrA 和 PpmA 在实验性 OM 中发挥互补作用。总之，我们使用压力舱开发了一种高度可重复且非侵入性的小鼠肺炎链球菌 OM 感染模型，非常适合研究肺炎链球菌在体内的发病机制和毒力。
