Biochemical tests can distinguish different types of bacteria by testing for the presence or activity of specific enzymes. Three common biochemical tests are: 1) The catalase test detects the presence of the catalase enzyme in bacteria by observing bubble formation when hydrogen peroxide is added. Bubbles indicate a positive result for bacteria like staphylococci. 2) The coagulase test identifies Staphylococcus aureus by detecting its coagulase enzyme, which clots plasma. A rapid clot is a positive result for S. aureus. 3) The oxidase test detects cytochrome c oxidase enzyme activity in bacteria by observing color change when the reagent tetramethyl-p-

1. Biochemical ID
Testing
Sawsan felmban

2. Different kinds of bacteria are
distinguished through….
Enzymes using biochemical tests

3. Biochemical tests
Test the ability, activity or
the presence of an
enzyme

4. Biochemical ID Testing
• Catalase test.
• Coagulase test.
• Oxidase test.

5. Catalase Test
• Reagents: H2O2
• Reaction :
• 2H2O2 catalase 2H2O + O2 (bubbles)
• Aim: to differentiate bacteria that produce catalase
enzyme.
Bubbles +ve Test QC:
(staphylococcus)
+ve cont.: Staphylococci spp.
results
No bubbles -ve -ve cont.: Streptococci spp.
(NOT staph.)

7. Coagulase Test
• Types of Coagulase:
• Free coagulase.
• Bound coagulase.
Reagent:
• Free coagulase: plasma containing coagulase reacting
factor (CRF).
• Bound coagulase: plasma
• Principle:
fibrinogen coagulase fibrin clot
Aim: to ID S. aureaus

8. • Results:
• Free coagulase: fibrin clot (within 2hrs, 4hrs and
24 hrs) +ve
• Bound coagulase: fibrin clot 10 sec +ve.
• No fibrin clot: -ve
• Test QC:
• +ve Cont.: Staph. aureus
• -ve Cont.: Staph. epidermidis

9. Free coagulase

10. Bound coagulase
posetive
negative
posetive negative

11. Oxidase Test
• Reagent:
• 1% tetramethyl-p-phenylenediamine
dihydrochloride.
• Principle:
• tetramethyl-p-phenylenediamine
dihydrochloride + reduced cytochrome c
oxidase oxidized cytochrome c (Purple) + H2O
• Aim:
to ID cytochrome oxidase producing bacteria

12. Oxidase Test
results
Dark purple : +ve
Pseudomonas
Colorless :
- ve others