The paradox in pneumococcal serotypes: highly invasive does not mean highly lethal

S treptococcus pneumoniae is a major bacterial pathogen and a predominant cause of community-acquired pneumonia, acute exacerbations of chronic bronchitis, meningitis, sinusitis and bacteraemia in both developed and developing countries. Each year millions of people die from pneumococcal diseases. Even in developed countries, the case-fatality rate of pneumococcal pneumonia is still high 1. This is in contrast to the fact that 1) appropriate antibiotic treatment is available, and 2) to date, antimicrobial resistance rates of pneumococci for non-meningeal infections are still low in most countries or antimicrobial resistance ( e.g. penicillin-resistance) is not related to treatment failure in pneumococcal pneumonia 2. A considerable number of patients die within the first 48 h and these early deaths have not been prevented by antibiotic treatment 3. Brueggemann et al. 4 investigated the risk of different pneumococcal serotypes to cause invasive disease. Invasive pneumococcal disease is defined as the isolation of S. pneumoniae from a normally sterile site, e.g. blood, cerebrospinal fluid or pleural fluid. The polysaccharide capsule protects pneumococci from phagocytosis and also may determine affinity to respiratory epithelium. Therefore, it seems reasonable that different pneumococcal …