Catalase Test

 Catalase Test

The catalase test is a biochemical test for aerobic organisms that detects the production of catalase enzyme in the organism.

Catalase enzyme is a common enzyme that is found in all living beings that survive in oxygen and catalyzes the decomposition of hydrogen peroxide, releasing water and oxygen.

Under the aerobic condition, 3% H2O2 is used, whereas 15% H2O2 is used under anaerobic conditions.

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Reagents and Supplies Used
Hydrogen peroxide reagent
  • 30% H2O2 for Neisseria
  • 15% H2O2 for anaerobes
  • 3% H2O2 for other bacteria (purchase or dilute 30% 1:10 in deionized water prior to use)
Supplies
  • Glass slide
  • Sterile wooden or glass sticks or platinum loops or wires

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Procedure of Catalase Test

There are more than one method or procedure variations for the catalase test. These methods include the slide or drop catalase test, the tube method, the heat-stable catalase used for the differentiation of Mycobacterium species, the semiquantitative catalase for the identification of Mycobacterium tuberculosis, and the capillary tube and coverslip method. The most popular method of catalase test in clinical bacteriology is the slide or drop catalase method as it requires a small number of organisms and works on a relatively uncomplicated technique.

 

1. Slide Method
  • A microscope slide is placed inside a petri dish. The use of a petri dish is optional and is used to limit catalase aerosols, which might carry viable bacterial cells.
  • A small amount of organism is collected from a well-isolated 18- to 24-hour colony with a sterile inoculating loop or wooden applicator stick and placed onto the microscope slide.
  • However, no agar must be picked up with the colony, especially when the culture is picked up from blood agar.
  • A drop of 3% H2O2 onto the organism on the microscope slide by using a dropper or Pasteur pipette.
  • The formation of bubbles is observed against a dark background to enhance readability.

 
2. Tube Method
  • About 4 to 5 drops of 3% H2O2 are added to a test tube.
  • Using a wooden applicator stick, a small amount of organisms from a well-isolated 18- to 24-hour colony is collected and placed into the test tube.
  • The tube is placed against a dark background and observed for immediate bubbles.

 

Quality Control

As a form of quality control, the following organisms can be used for positive and negative results:

  1. Staphylococcus aureus: Catalase positive.
  2. Streptococcus pyogenes: Catalase-negative.
 
Result and Interpretation of Catalase Test
  • The positive test is demonstrated by the immediate appearance of bubbles.
  • The appearance of one or two bubbles represents a weak reaction.
  • A negative test is represented by no bubbles or a few bubbles after 20 s.
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