Podcast
Questions and Answers
What role does the oxidase reagent play in the oxidase test?
What role does the oxidase reagent play in the oxidase test?
The oxidase reagent, specifically 1% tetramethyl-p-phenylenediamine dihydrochloride, detects the presence of cytochrome c oxidase by turning the bacteria violet to purple.
Explain why delayed reactions should be ignored in the oxidase test.
Explain why delayed reactions should be ignored in the oxidase test.
Delayed reactions are disregarded because they may indicate false positives, leading to inaccurate identification of the bacterial species.
Describe the expected result in a positive oxidase test.
Describe the expected result in a positive oxidase test.
A positive oxidase test is indicated by the development of a dark purple color (indophenols) within 10 seconds.
List the four methods for performing the oxidase test.
List the four methods for performing the oxidase test.
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Why are positive and negative control organisms used in the oxidase test?
Why are positive and negative control organisms used in the oxidase test?
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The oxidase reagent used in the test is 1% tetramethyl-p-phenylene-________ dihydrochloride.
The oxidase reagent used in the test is 1% tetramethyl-p-phenylene-________ dihydrochloride.
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For a positive reaction, the bacteria should turn ________ to purple within 10 to 30 seconds.
For a positive reaction, the bacteria should turn ________ to purple within 10 to 30 seconds.
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Using a sterile swab, obtain a small amount of organism from an agar ________ or plate.
Using a sterile swab, obtain a small amount of organism from an agar ________ or plate.
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In the oxidase test, the absence of color indicates a ________ result.
In the oxidase test, the absence of color indicates a ________ result.
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The preferred method for conducting the oxidase test is the dry filter paper ________.
The preferred method for conducting the oxidase test is the dry filter paper ________.
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Study Notes
Oxidase Test Procedure
- Equipment needed includes a safety cabinet and Bunsen burner.
- Materials required are pointed glass rods, sterile filter paper, and 1% tetramethyl-p-phenylenediamine dihydrochloride reagent.
- Specimens are well-isolated bacterial colonies.
- Positive control organism: Pseudomonas aeruginosa.
- Negative control organism: Proteus sp.
Methods
- Several methods exist for the oxidase test:
- Dry filter paper method
- Wet filter paper method
- Cotton-tipped stick method
- Plate method
Dry Filter Paper Method
- Obtain a small amount of bacteria from an agar slant or plate using a sterile swab.
- Apply one drop of oxidase reagent to the bacteria on the swab.
- A positive reaction displays a rapid change, turning the bacteria a dark purple colour within 10-30 seconds.
- Ignore any delayed reactions.
Observation
- Positive result: Dark purple colour develops within 10 seconds (indophenols).
- Negative result: Absence of colour change.
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Description
Test your knowledge on the oxidase test procedure, including the equipment, materials, and methods used in the test. This quiz covers important aspects of performing the oxidase test, identifying positive and negative reactions, and understanding control organisms.
