The Transforming Streptococcus Pneumoniae in the 21st Century

Streptococcus pneumoniae, an important pathogen causingsepsis, sinusitis, otitis media, bacterial meningitis and bacterialpneumonia, results in global morbidity and mortality eachyear. The burden of pneumococcal disease is highest in childrenand the elderly. Treatment of pneumococcal infection hasbeen hampered by the complexity of the host immuneresponse. In recent decades, the increase of S. pneumoniaestrains’ resistance to β-lactam antibiotics and other classes ofantimicrobials has made treatment even more complicated.Fortunately, the advent of heptavalent conjugate vaccine confersa high degree of protection against pneumococcal diseaseand colonization caused by vaccine serotype strains. After theintroduction of conjugate pneumococcal vaccine, invasivepneumococcal disease caused by vaccine serotypes and antibiotic-resistant isolates has been reduced. However, naturallytransformable pneumococci may escape vaccine-induced immunity by switching their capsulargenes to non-vaccine serotypes. Development of cheaper, serotype-independent vaccinesbased on a combination of protein antigens should be pursued.