Oxidase Test: Click Here to View Images
The oxidase test is a test for the presence of the enzyme cytochrome
oxidase. In the presence of this enzyme, the oxidase reagent (N,N,N',N'-
tetramethyl-p-phenylenediamine dihydrochloride) is oxidized and turns from
colorless to purple.
Tips for Success:
Only perform the oxidase test on fresh cultures. Using older cultures may
yield unexpected results. The color change should occur within the first 30
seconds. Disregard any color changes after this time period. Do not use a
nichrome loop as this may lead to a false-positive result. Always run
positive and negative controls from known cultures
Procedure:
The oxidase test is a test for the presence of the enzyme cytochrome
oxidase. In the presence of this enzyme, the oxidase reagent (N,N,N',N'-
tetramethyl-p-phenylenediamine dihydrochloride) is oxidized and turns from
colorless to purple.
Tips for Success:
Only perform the oxidase test on fresh cultures. Using older cultures may
yield unexpected results. The color change should occur within the first 30
seconds. Disregard any color changes after this time period. Do not use a
nichrome loop as this may lead to a false-positive result. Always run
positive and negative controls from known cultures
Procedure:
- Place a piece of filter paper on a clean microscope slide.
- Place 2 to 3 drops of oxidase reagent onto the filter paper
- Touch an isolated colony with a wooden applicator stick
- Place the end of the stick, carrying some of the isolate, onto the
reagent saturated filter paper. - Observe for the presence of a dark purple color
- The reaction is positive if the smear turns purple within 10-30
seconds.
| Oxidase Procedure For The Identification of Bacteria |
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