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Streptococcus pneumoniae pneumococus

Streptococcus pneumoniae pneumococus. Pneumonia Meningitis bacteraemia. Description . Gram-positive diplococci (in pairs) Encapsulated ovoid or lanceolate coccus Non-motile Fastidious (enriched media) Blood or chocolate agar 5-10 % CO2 Alpha haemolysis + draughtsman appearance

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Streptococcus pneumoniae pneumococus

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  1. Streptococcus pneumoniaepneumococus Pneumonia Meningitis bacteraemia

  2. Description • Gram-positive diplococci (in pairs) • Encapsulated ovoid or lanceolate coccus • Non-motile • Fastidious (enriched media) • Blood or chocolate agar • 5-10 % CO2 • Alpha haemolysis + draughtsman appearance • Some strains are mucoid • Soluble in bile • Optochin sensitive

  3. Pathogenesis • Virulence factors • Capsular polysaccharide • The major factor • 84 serotypes • Both antigenic and type specific • Antiphagocytic • Serotype 3 , 7 are most virulent • 90% of cases of bacteraemic pneumococcal pneumonia and meningitis are caused by 23 serotypes • Quellung reaction , india ink • Pneumolysin • Membrane damaging toxin

  4. Carrier rate • Oropharyngeal flora of 5 – 70% of the population • Significance in respiratory infection

  5. Predisposing factors Aspiration of upper airway secretions ( endogenous ) No person-person spread Disturbed consciousness , general anaesthesia , convulsions , CVA , epilepsy , head trauma Prior LRT. VIRAL infection Preexisting respiratory diseases , smoking Chronic bronchitis , bronchogenic malignancy Chronic heart disease Chronic renal disease ( nephrotic syndrome ) Chronic liver disease ( cirrhosis) Diabetes mellitus Old age , (extreme of age ) Malnutrition , alcoholism

  6. Specific deficiencies in host defence • Hypogamaglobulinaemia • Asplenia , hypospenism ( tuftsin ) • Homozygous sickle cell disease • Coeliac disease • Multiple myeloma , leukaemia , lymphomas • Neutropenia • HIV Relative or absolute deficiency of opsonic antibody or inadequate manufacture of type specific antibody

  7. Diseases • Respiratory tract infections • Lobar pneumonia ( commonest cause of CAP ) • Empyema • Otitis media (6 months – 3 yrs ) • Mastoiditis • Sinusitis • Acute exacerbation of chronic bronchitis • Meningitis • Conjunctivitis • Peritonitis ( primary ) • Bacteraemia ( 15 % of pneumonia ) • septicaemia

  8. Clinical feature • Lobar pneumonia • Sudden onset • Fever • rigor • Cough , rusty sputum • Pleural pain • Signs of lobar consolidation • Polymorphonuclear leucocytosis • Empyema , pericarditis

  9. Meningitis • The most virulent pathogen of meningitis • Mortality ( 20% ) • Primary • Complicate infections at other site ( lung ) • Bacteraemia usually coexists • Bimodal incidence ( < 3 yr - > 45 yr )

  10. Mortality • Age (> 65 yr ) • Preexisting disease • Bacteraemia • Serotype 3 , 7

  11. Laboratory diagnosis • Specimen • Sputum • CSF • Swabs • Pus • Blood culture • Aspirate

  12. Microscopy • Gram stained smear • Gram-positive diplococci + pus cells • culture • Blood agar , chocolate agar + 10 % CO2 • identification • Alph-haemolytic colonies • Optochin sensitive • Bile soluble

  13. Sensitivity testing • Penicillin • susceptible • Sensitive • Nonsusceptible • Intermediate • Resistant • Ampicillin , amoxicillin • Erythromycin • Ceftriaxone , cefuroxime • Clindamycin • Fluroquinolones • tetracyclines • Vancomycin

  14. Treatment • Meningitis • Parenteral ceftriaxone + vancomycin • pneumonia • Outpatients • Erythromycin • Amoxacillin – clavulanic acid • Cefuroxime or ceftriaxone (IV) + oral b- lactam • Inpatients • Parenteral cefuroxime or ceftriaxone

  15. Prevention • 23 polysaccharide vaccine • Not effective in children < 2 yrs • >65 yrs • Functional or anatomical asplenia • SCD • 7-valent – protein- conjugated vaccine • Children < 3 yrs

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