Strep pneumoniae: Overview
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Streptococcus pneumoniae Overview
- Gram + cocci in pairs (diplococci)
- Lancet-shaped
- Alpha-hemolytic
- partial or “green” hemolysis on blood agar
- Encapsulated
- Causes bacteremia/sepsis in patients with sickle cell disease (functional asplenia) vs. asplenic patients
- Main virulence factor; not pathogenic without capsule
- IgA protease
- cleaves lgA at its hinge region (yielding Fab and compromised Fc fragments)
- Reduced functional IgA increases bacterial adherence to mucosal membranes
- Bile-soluble
- Exhibits cell lysis in the presence of bile
- In contrast vs. strep viridans, which is bile-resistant
- Optochin sensitive
- In contrast vs. strep viridans, which is optochin-resistant