BACKGROUND The polysaccharide capsule is a major virulence factor of S. pneumoniae in diseases such as meningitis. While some capsular serotypes are more often found in invasive disease, high case fatality rates are associated with those serotypes more commonly found in asymptomatic colonization. We tested whether growth patterns and capsule size in human cerebrospinal fluid depends on serotype using a clinical isolate of S. pneumoniae and its capsule switch mutants. RESULTS We found that the growth pattern differed markedly from that in culture medium by lacking the exponential and lysis phases. Growth in human cerebrospinal fluid was reduced when strains lost their capsules. When a capsule was present, growth was serotype-specific: high carriage serotypes (6B, 9 V, 19F and 23F) grew better than low carriage serotypes (7F, 14, 15B/C and 18C). Growth correlated with the case-fatality rates of serotypes reported in the literature. Capsule size in human cerebrospinal fluid also depended on serotype. CONCLUSIONS We propose that serotype-specific differences in disease severity observed in meningitis patients may, at least in part, be explained by differences in growth and capsule size in human cerebrospinal fluid. This information could be useful to guide future vaccine design.

中文翻译：

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肺炎球菌血清型决定人脑脊髓液中的生长和胶囊大小。

背景技术多糖胶囊是诸如脑膜炎之类的肺炎链球菌的主要毒力因子。虽然某些荚膜血清型在侵袭性疾病中更常见，但高病死率与无症状定植中更常见的那些血清型有关。我们使用临床分离的肺炎链球菌及其胶囊开关突变体，测试了人脑脊髓液中的生长方式和胶囊大小是否取决于血清型。结果我们发现，由于缺乏指数期和裂解期，其生长模式与培养基中的生长模式显着不同。当菌株丢失其胶囊时，人脑脊液中的生长减少。当有胶囊存在时，生长是血清型特异性的：高马力血清型（6B，9 V，19F和23F）比低马力血清型（7F，14、15B / C和18C）生长得更好。生长与文献报道的血清型的病死率相关。人脑脊髓液中的胶囊大小也取决于血清型。结论我们建议在脑膜炎患者中观察到的疾病严重程度的血清型特异性差异可以至少部分地由人脑脊液生长和胶囊大小的差异来解释。该信息可能对指导将来的疫苗设计很有用。