Hathaway Lucy J, Grandgirard Denis, Valente Luca G, Täuber Martin G, Leib Stephen L
Institute for Infectious Diseases, Faculty of Medicine, University of Bern, Bern 3001, Switzerland
Institute for Infectious Diseases, Faculty of Medicine, University of Bern, Bern 3001, Switzerland.
Open Biol. 2016 Mar;6(3). doi: 10.1098/rsob.150269.
Streptococcus pneumoniaebacteria can be characterized into over 90 serotypes according to the composition of their polysaccharide capsules. Some serotypes are common in nasopharyngeal carriage whereas others are associated with invasive disease, but when carriage serotypes do invade disease is often particularly severe. It is unknown whether disease severity is due directly to the capsule type or to other virulence factors. Here, we used a clinical pneumococcal isolate and its capsule-switch mutants to determine the effect of capsule, in isolation from the genetic background, on severity of meningitis in an infant rat model. We found that possession of a capsule was essential for causing meningitis. Serotype 6B caused significantly more mortality than 7F and this correlated with increased capsule thickness in the cerebrospinal fluid (CSF), a stronger inflammatory cytokine response in the CSF and ultimately more cortical brain damage. We conclude that capsule type has a direct effect on meningitis severity. This is an important consideration in the current era of vaccination targeting a subset of capsule types that causes serotype replacement.
肺炎链球菌可根据其多糖荚膜的组成分为90多种血清型。一些血清型在鼻咽部携带中很常见，而其他血清型则与侵袭性疾病有关，但当携带血清型发生侵袭时，疾病往往特别严重。尚不清楚疾病的严重程度是直接归因于荚膜类型还是其他毒力因子。在此，我们使用一株临床肺炎球菌分离株及其荚膜转换突变体，在与遗传背景分离的情况下，确定荚膜对幼鼠模型中脑膜炎严重程度的影响。我们发现拥有荚膜是导致脑膜炎的必要条件。6B血清型比7F血清型导致的死亡率显著更高，这与脑脊液（CSF）中荚膜厚度增加、CSF中更强的炎性细胞因子反应以及最终更多的皮质脑损伤相关。我们得出结论，荚膜类型对脑膜炎严重程度有直接影响。在当前针对导致血清型替换的部分荚膜类型进行疫苗接种的时代，这是一个重要的考虑因素。
