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Catalase Test

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Abstract or Description:

 

Description
Detects the presence of te enzyme catalase which hydrolyzes H2O2 to produce H2O and O2. This test is used to differentiate Staphylococci (catalase positive) from Streptococci (catalase negative).


Procedure
Pick a colony from an 18-24 hour culture and place it on a clean glass slide. Avoid carry over of blood agar which cna cause false positives.


Put one drop of 3% H2O2 over the organism on the slide. Do not reverse the order of the procedure as false positive results may occur. Do not mix.


Observe for immediate bubbling (gas liberation) and record the result.


Discard the slide into a discard container.
Interpretation



Positive test: Immediate bubbling, easily observed (O2 formed)

Negative test: No bubbling.

Precautions

Carry over of blood agar must be avoided.


Growth for testing must be from an 18-24 hour culture.


3% H2O2 is caustic - avoid exposure to skin. If H2O2 does get on the skin, immediately flood the area with 70% ethyl alcohol, not water.


Aerosols may be released by the bubbling of the O2.


H2O2 is unstable and breaks down easily on exposure to light. The solution must be kept refrigerated in the dark.



Recipes
Hydrogen peroxide (H2O2), 3%
Store in a dark bottle and avoid any undue exposure to light.
Keep refrigerated at all times when not in use.

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Posted By: pundir on 1/20/2009 5:05:04 AM
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