Streptococcus pneumoniae: The Prototype of Lung Responses in Pneumonia

Abstract

Streptococcus pneumoniae causes infections as diverse as meningitis, sepsis, and otitis media, but its species name “pneumoniae” refers to its dominant role in pneumonia. Pneumonia is broadly divided into three classes: community-acquired, hospital-acquired, and pneumonia in an immunocompromised host (Reynolds et al. 2010; Watson et al. 1993). Since its initial identification by Louis Pasteur and George Sternberg over 130 years ago, S. pneumoniae remains the leading causative agent of community-acquired pneumonia worldwide (Watson et al. 1993). Host immune responses must contend with over 90 pneumococcal capsular serotypes. Children <2 years old who lack the ability to mount effective immunoglobulin responses to capsular antigens are the most susceptible to invasive pneumococcal disease (Reynolds et al. 2010). Lobar pneumonia, a classic description in clinical medicine, presents with five cardinal signs: sudden onset chest pain, a shaking chill, cough, fever, and production of blood tinged sputum (Heffron 1939). In pediatric patients, presenting symptoms include fever, cough, labored breathing with grunting, and cyanosis (Tan et al. 1998). In adults, community-acquired pneumococcal pneumonia often presents with opacity in a lobar pattern on chest radiographs (Reynolds et al. 2010). In both children (Don et al. 2010) and adults (Cilloniz et al. 2011), most cases of pneumococcal pneumonia resolve after treatment with a 5 % mortality rate. However, complications such as pleural effusion, empyema, and multi-lobar consolidation can arise (Cilloniz et al. 2011).