Streptococcus pneumoniae

Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, alpha-hemolytic, facultative anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.

S. pneumoniae resides asymptomatically in the nasopharynx of healthy carriers. The respiratory tract, sinuses, and nasal cavity are the parts of host body that are usually infected. However, in susceptible individuals, such as elderly and immunocompromised people and children, the bacterium may become pathogenic, spread to other locations and cause disease. S. pneumoniae is the main cause of community acquired pneumonia and meningitis in children and the elderly, and of septicemia in HIV-infected persons. The methods of transmission include sneezing, coughing, and direct contact with an infected person.

Despite the name, the organism causes many types of pneumococcal infections other than pneumonia. These invasive pneumococcal diseases include bronchitis, rhinitis, acute sinusitis, otitis media, conjunctivitis, meningitis, bacteremia, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess.