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Morphology
- Gram positive oval cocci arranged in pairs (lancet/bullet shape)
- Surface capsule -> polysaccharide polymers (unique for each serotype)
- Grows on blood agar with alpha-hemolysis
- bile solubility test
- Pneumolysin: pore forming toxin
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Epidemiology
- Leading cause of pneumonia, acute purulent meningitis, bacteremia
- Otitis media
- Usually in young and older person
- Usually present in nasopharynx
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Pathogenesis
- Aspiration of respiratory secretions containing the bacteria
- COPD, respiratory dysfunction from alcoho, narcotics, trauma, etc increase the risk of infection
- Alveolar infection: surface capsule blocks phagocytosis via complement inhibition; pneumolysin damages tissue
- Capsule: Major determinant of virulence
- Pneumolysin: destroys respiratory epi cells which aids in reaching the alveolus
- Immunity: type specific
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Clinical manifestations
- Pneumonia: Shaking chill and high fever, cough with rusty sputum, pleurotic chest pain; lobar consolidation
- meningitis: most common at advanced age
- Does not cause pharyngitis or tonsillitis
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Diagnosis
- Routine culture
- Susceptibility Optochin
- Bile solution
- Blood cultures valuable
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Treatment
- Penicillin G
- Resistance via changes in transpeptidases
- Penicillinase not produced
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Prevention
- Conjugate vaccine
- Adult: 23 serotypes
- Kids: 13 (below 2 YO)
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