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WEEK 8

WEEK 8. Identification of Staphylococci and Streptococci. Exercise 1: Catalase Test. Used to differentiate between Staphylococci and Streptococci Test for Catalase – an enzyme that breaks down hydrogen peroxide If bubble form, it is a positive for catalase

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WEEK 8

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  1. WEEK 8 Identification of Staphylococci and Streptococci

  2. Exercise 1: Catalase Test • Used to differentiate between Staphylococci and Streptococci • Test for Catalase – an enzyme that breaks down hydrogen peroxide • If bubble form, it is a positive for catalase • Staphylococci is catalase positive whereas streptococci is negative

  3. Exercise 2: Coagulase • Allows us to differentiate between different forms of Staphylococci • Coagulase is an enzyme produced by Staphylococci Aureus and not the other forms of Staphylococci • Forms plasma clots around itself for protection

  4. Exercise 3: Mannitol Salt Agar (MSA) • Allows us to differentiate between different forms of Staphylococci • Selective for Staphylococci • Differential for pathogenic form Staph. Aureus • Looking for fermentation of mannitol (yellow)

  5. Exercise 4: Novobiocin Sensitivity Test • Used to differentiate between different forms of Staphylococci bacteria • Novobiocin is an antibiotic • S. saprophyticus is resistant to novobiocin, while S. aureus and S. epidermidis are susceptible

  6. Exercise 5: Hemolysis • Used to determine the species of Streptococci • Enzyme called Hemolysin • Beta-hemolytic streptococci completely hydrolyze red blood cells • Alpha-hemolytic streptococci partially hydrolyze red blood cells • gamma-hemolytic (or Non-hemolytic) are not hemolytic at all and do not affect the red blood cells

  7. Exercise 6: Bacitracin Sensitivity • Used to determine the species of Streptococci • Bacitracin is an antibiotic

  8. Exercise 7: Bile Esculin Test • Used to determine the species of Streptococci • Plate contains bile, which inhibits the growth of organisms except Group D streptococci and enterococci • Group D streptococci and enterococci can hydrolyze esculin into glucose and esculetin. • The glucose is used for energy metabolism and the esculetin reacts with iron salts in the media to form a black precipitate which verifies presence of a Group D strep or enterococci

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