Lecture 4 Strep. pneumoniae

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Lecture 4 Strep. pneumoniae

  1. 1. ‫بسم ا الرحمن الرحيم‬ Streptococcus pneumoniae Prof. Khalifa Sifaw Ghenghesh
  2. 2. Diplococcus pneumoniae or Pneumococcus Gram +ve Coccus, Encapsulated, Occur in Pairs with Broad Ends Opposed. Requires Enriched Media for Growth. Growth Enhanced by 0.1% Glucose and 5-10% CO2.
  3. 3. Streptococcus pneumoniae
  4. 4. Colonies on Blood Agar 1 mm in Diameter, Round, Domed and Surrounded by a Zone of α-Haemolysis. On Prolonged Incubation: "Draughtsman" Colonies. Some Strains > Mucoid Colonies. In Broth > Short Chains or Isolated Cocci. Soluble in Bile. Sensitive to Optochin (Ethylhydrocuprein Hydrochloride).
  5. 5. VIRULENCE FACTORS Capsular Polysacharide > Antiphagocytic. – Repeated Subculturing in the Presence of Specific Anticapsular Antibody Results in NonCapsulated Strains. Non-Capsulated Strains > Avirulent > "R" Colonies. "S" Colonies >> Virulent. Capsule Can Be Demonstrated by: 1. "Quelling Reaction" or “Capsular Swelling Test”: 2. Addition of India Ink:
  6. 6. CLINICAL INFECTION Pneumococcal Infections of the Respiratory Tract. Causes Disease of the Middle Ear, Paranasal Sinuses, Mastoides and the Lung Paranchyma. Meningitis, Endocarditis and Peritonitis. Pneumococcal Bacteraemia.
  7. 7. Pneumococcal Meningitis
  8. 8. LABORATORY DIAGNOSIS 1. Specimens: Sputum: i. Should Show a Predominance of Pus Cells Rather Than Squamous Epithelial Cells of Buccal Origin. ii. The Specimen is Then Homogenized by an Agent (e.g. N-Acetylcysteine). CSF Deposit: From Cases of Meningitis. Blood: Patients with Pneumococcal Pneumonia and Meningitis.
  9. 9. 2. Isolation and Identification: Gram Stain BA Incubate in 5-10% CO2/ Overnight α - Haemolytic Colonies Susceptibility to Optochin Sensitive >> Strep. Pneumoniae Resistant >> Strep. viridans
  10. 10. TREATMENT Penicillins, Cephalosporins, Erythromycin, Tetracycline, Clindamycin, Vancomycin and Ciprofloxacin. Resistance:
  11. 11. Streptococcus viridans

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