Pneumococci

Streptococcus pneumoniae
S. pneumoniae in spinal fluid. FA stain (digitally colored).
Scientific classification
Domain:	Bacteria
Phylum:	Firmicutes
Class:	Cocci
Order:	Lactobacillales
Family:
Genus:
Species:	S. pneumoniae
Binomial name
Streptococcus pneumoniae (Klein 1884) Chester 1901

Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), facultative anaerobic member of the genus . As 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 healthy carriers typically colonizing the respiratory tract, sinuses, and nasal cavity. However, in susceptible individuals with weaker immune systems, such as the elderly and young children, the bacterium may become pathogenic and spread to other locations to cause disease.

S. pneumoniae is the main cause of community acquired pneumonia and meningitis in children and the elderly, and of septicemia in those infected with HIV. The organism also causes many types of pneumococcal infections other than pneumonia. These invasive pneumococcal diseases include bronchitis, rhinitis, acute sinusitis, otitis media, conjunctivitis, meningitis, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess.

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