15 Pneumococcal disease

15.1 Bacteriology

Streptococcus pneumoniae is a gram-positive diplococcus. It is ubiquitous, and many individuals carry the organism asymptomatically in their upper respiratory tract. There are over 90 identifiable serotypes of S. pneumoniae. Certain serotypes are more invasive or more associated with antibiotic resistance, and dominant serotypes vary by age and geographical distribution.