Introduction of Catalase Test
Catalase test is used to differentiate those bacteria that produce this enzyme, such as staphylococci, from non-catalase producing bacteria such as streptococci.
Principle of Catalase Test
Catalase acts as a catalyst in the breakdown of hydrogen peroxide into nascent oxygen and water. This nascent oxygen causes bubbling. An organism is tested for catalase production by bringing it into contact with hydrogen peroxide. Bubbles of oxygen are released if the organism is a catalase producer.
Requirements for Catalase Test
- Test organism
- 3% Hydrogen peroxide (H2O2)
- sterile bamboo sticks
- Test tubes
- Slides ( for slide method)
- Quality control (QC) strains for negative control and positive Control
Procedure of Catalase Test-Slide Method
- Take a drop of the hydrogen peroxide solution into a sterile grease-free glass slide.
- Using a sterile bamboo stick or a glass rod or coverslip pick up a colony of the test organism and immerse them in the hydrogen peroxide solution.
- Look for immediate bubbling as shown in figure
Procedure of Catalase Test-Tube Method
- Pour 2–3 ml of the hydrogen peroxide solution into a test tube.
- Using a sterile bamboo stick or a glass rod remove several colonies of the test organism and immerse them in the hydrogen peroxide solution.
- Look for immediate bubbling.
Result Interpretation of Catalase Test
Active bubbling – Positive
No bubbles – Negative
Positive control (PC): Staphylococcus aureus (ATCC25923)
Negative control (NC): Streptococcus pyogenes (ATCC 19615)
Uninoculated (UN): No organism only 3% H2O2
- Care must be taken when testing a bacterium cultured on a medium containing blood because catalase is present in red blood cells. If any of the blood agar is removed from the organism, a false-positive reaction may occur.
- A Nichrome wire loop is not recommended to pick up the colonies.
- Performing the test on a slide is not recommended because of the risk of contamination from active bubbling. When the rapid slide technique is used, the hydrogen peroxide solution should be added to the bacterial suspension after placing the slide in a Petri plate. The plate should then be covered immediately, and the preparation observed for bubbling through the lid.
- The culture should not be more than 24 hours old.
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