1. Identification of Staphylococci and Streptococci
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