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Practical Medical Microbiology

Practical Medical Microbiology. Lab # 3 Laboratory Identification of streptococci. Microscopic examination. Morphological Description: Type of stain: Gram stain Gram reaction: Gram +ve Color: Violet Shape: Cocci Size: Small

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Practical Medical Microbiology

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  1. Practical Medical Microbiology Lab # 3 Laboratory Identification of streptococci

  2. Microscopic examination Morphological Description: • Type of stain: Gram stain • Gram reaction: Gram +ve • Color: Violet • Shape: Cocci • Size: Small • Arrangement: Chains or pairs

  3. Culture MEDIA Culture media for streptococci: • Blood agar • Chocolate agar

  4. Culture MEDIA

  5. Culture MEDIA

  6. Biochemical reactions and confirmatory tests • Blood hemolysis:α, β, γ • Biochemical tests: 1. Bile solubility 2. Bacitracin sensitivity 3. Optochin sensitivity • Serological test:Antistreptolysin O test (ASO)

  7. 1-Hemolysis on blood agar (ɑ) Partial hemolysis (β) Complete hemolysis (γ) No hemolysis S. faecalis & S. epidermidis S. pneumoniae & Viridans streptococci S. pyogenes & S. aureus Hemoglobin Met-Hemoglobin

  8. 2-Bile solubility To differentiate between ɑ-hemolytic streptococci: S. pneumoniae and viridans Nutrient broth + bile salts S. pneumoniae Viridans Resistant Lysis No lysis Sensitive Viridans S. pneumoniae

  9. 3- Bacitracin sensitivity To differentiate between β-hemolytic S. pyogenes& ɑ, γ -hemolytic S. pneumoniaeand viridans Resistant Sensitive Bacitracin antibiotic disc S. Pneumoniae & Viridans S. pyogenes

  10. 4- Optochin sensitivity To differentiate between ɑ-hemolytic streptococci: S. pneumoniae and viridans Optochin sensitive Optochin resistant S. pneumoniae Viridans streptococci Optochin = Ethyl hydrocupreinHCl

  11. Anti-streptolysin O (ASO) test Detection of anti-streptolysin O antibody in patient’s serum as an indication for streptococcal infection Polystyrene latex beads coated with Streptolysin O antigen Ab Patient serum +ve agglutination

  12. Required Spots for lab#3

  13. Spots Blood agar Potential Questions • Mention type of medium • What are the constituents of the medium? • What is the use of the medium?

  14. Spots Chocolate agar Potential Questions • Mention type of medium • What are the constituents of the medium? • What is the use of the medium?

  15. Spots Potential Questions • What is the name of medium? • What is the type of medium? • What is the type of hemolysis? • Name of the microorganism giving this result • What is the use of this test? (β) Complete hemolysis Hemolysis on blood agar S. pyogenes & S. aureus

  16. Spots Potential Questions • What is the name of medium? • What is the type of medium? • What is the type of hemolysis? • Name of the microorganism giving this result • What is the use of this test? Hemolysis on blood agar (γ) No hemolysis S. faecalis & S. epidermidis

  17. Spots Potential Questions • What is the composition of medium? • Name of the microorganism giving the result in (A) & (B)? • What is the use of this test? A B Bile solubility test Sensitive Resistant S. pneumoniae Viridans

  18. Spots Potential Questions • What is the name of the antimicrobial? • Name of the microorganism giving the result in (A) & (B)? • What is the use of this test? Optochin sensitivity A S. pneumoniae B Viridans streptococcus

  19. Spots Potential Questions • What is the principle of the test? • Name the result in (A) & (B)? • What is the use of this test? ASO test A B

  20. Thank YOU Next lab: Enterobacteriaceae 1

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