Oxidase test: Difference between revisions
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==Background== |
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= Oxidase test = |
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* Identifies '''cytochrome C oxidase''' by testing for the ability to oxidize tetramethyl-p-phenylenediamine to indophenols, which are purple |
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* The test is positive when it turns '''purple''' within 10 seconds |
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** Must be done from plain 5% SBA |
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The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. When present, the '''cytochrome c oxidase''' oxidizes the reagent '''(tetramethyl-p-phenylenediamine)''' to '''(indophenols)''' purple color end product. When the enzyme is not present, the reagent remains reduced and is colorless. |
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* All oxidase-positive bacteria are aerobic |
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** '''N''': [[Neisseria]] |
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===Oxidase-Positive Organisms=== |
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[https://i2.wp.com/microbeonline.com/wp-content/uploads/2012/12/Oxidase-test-result.gif [[File:https://i2.wp.com/microbeonline.com/wp-content/uploads/2012/12/Oxidase-test-result.gif?resize=280%2C225|Oxidase test result]]] |
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{{#ask: [[Oxidase::positive]] |?Stain |?Cellular shape |?Oxidase }} |
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===Oxidase-Negative Organisms=== |
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'''Note:''' All bacteria that are oxidase positive are aerobic, and can use oxygen as a terminal electron acceptor in respiration. This does NOT mean that they are strict aerobes. Bacteria that are oxidase-negative may be anaerobic, aerobic, or facultative; the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent. They may respire using other oxidases in electron transport. |
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{{#ask: [[Oxidase::negative]] |?Stain |?Cellular shape |?Oxidase }} |
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== Further Reading == |
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'''Test requirements for Oxidase test:''' Moist filter paper with the substrate (1% tetramethyl-p-phenylenediamine dihydrochloride), or commercially prepared paper disk, wooden wire or platinum wire. |
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* Microbe Online. [https://microbeonline.com/oxidase-test-principle-procedure-and-oxidase-positive-organisms/ Oxidase Test: Principle, Procedure and Oxidase-Positive Organisms]. |
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[[Category:Diagnostics]] |
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== Procedure == |
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# Take a filter paper soaked with the substrate tetramethyl-p-phenylenediamine dihydrochloride |
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# Moisten the paper with a sterile distilled water |
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# Pick the colony to be tested with wooden or platinum loop and smear in the filter paper |
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# Observe inoculated area of paper for a color change to deep blue or purple within 10-30 seconds |
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=== Precautions === |
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# Do not use Nickel-base alloy wires containing chromium and iron (nichrome) to pick the colony and make smear as this may give false positive results |
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# Interpret the results within 10 seconds, timing is critical |
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# The oxidase test must be performed from 5% Sheep blood agar or another medium without a fermentable sugar . Fermentation of a carbohydrate results in acidification of the medium (e.g., lactose in [https://microbeonline.com/macconkey-agar-mac-composition-preparation-uses-and-colony-characteristics/ MacConkey Agar] or Sucrose in [https://microbeonline.com/thiosulfate-citrate-bile-salts-sucrose-tcbs-agarcomposition-uses-colony-characteristics/ TCBS]), and a false negative oxidase test may result if the surrounding pH is below 5.1. |
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# During identification of suspected ''Vibrio cholerae'' isolate, it is not possible to perform an oxidase test directly from a '''TCBS culture''' because the acid produced by the sucrose fermenting colonies will inhibit the oxidase reaction. |
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# '''Positive:''' Development of '''dark purple color''' (indophenols) within 10 seconds |
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# '''Negative:''' Absence of color |
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Bacterial genera characterized as oxidase positive include ''Neisseria'' and ''Pseudomonas''. Genera of the[https://microbeonline.com/seven-common-characteristics-family-enterobacteriaceae/ Enterobacteriaceae ]family are characterized as '''oxidase negative.''' |
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'''Name of Oxidase positive bacteria are:''' '''PVNCH''' |
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# '''N''': [https://microbeonline.com/neisseria-gonorrhoeae-properties-disease-pathogenesis-and-laboratory-diagnosis/ ''Neisseria''] spp. |
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# Alcaligens |
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Latest revision as of 02:52, 8 February 2022
Background
- Identifies cytochrome C oxidase by testing for the ability to oxidize tetramethyl-p-phenylenediamine to indophenols, which are purple
- The test is positive when it turns purple within 10 seconds
- Must be done from plain 5% SBA
Interpretation
- All oxidase-positive bacteria are aerobic
- P: Pseudomonas
- V: Vibrio cholerae
- N: Neisseria
- C: Campylobacter
- H: Helicobacter and Haemophilus
- Aeromonas
Oxidase-Positive Organisms
| Stain | Shape | Oxidase | |
|---|---|---|---|
| Achromobacter | Gram-negative | bacillus | positive |
| Aeromonas | Gram-negative | bacillus | positive |
| Alcaligenes faecalis | Gram-negative | bacillus | positive |
| Brucella melitensis | Gram-negative | coccobacillus | positive |
| Burkholderia pseudomallei | Gram-negative | bacillus | positive |
| Campylobacter | Gram-negative | bacillus | positive |
| Francisella tularensis | Gram-negative | coccobacillus | positive negative |
| Helicobacter pylori | Gram-negative | bacillus | positive |
| Herbaspirillum | Gram-negative | bacillus | positive |
| Micrococcus | Gram-positive | coccus | positive |
| Moraxella catarrhalis | Gram-negative | diplococcus | positive |
| Neisseria | Gram-negative | diplococcus | positive |
| Ochrobactrum anthropi | Gram-negative | bacillus | positive |
| Pasteurella | Gram-negative | bacillus | positive |
| Pseudomonas aeruginosa | Gram-negative | bacillus | positive |
| Vibrio | Gram-negative | bacillus | positive |
| Vibrio cholerae | Gram-negative | bacillus | positive |
| Vibrionaceae | Gram-negative | bacillus | positive |
Oxidase-Negative Organisms
| Stain | Shape | Oxidase | |
|---|---|---|---|
| Acinetobacter ursingii | Gram-negative | coccobacillus | negative |
| Cronobacter sakazakii | Gram-negative | bacillus | negative |
| Erysipelothrix rhusiopathiae | Gram-positive | bacillus | negative |
| Francisella tularensis | Gram-negative | coccobacillus | positive negative |
| Listeria monocytogenes | Gram-variable Gram-positive | bacillus pleomorphic | negative |
| Proteus | Gram-negative | bacillus | negative |
| Raoultella | Gram-negative | bacillus | negative |
| Raoultella ornithinolytica | Gram-negative | bacillus | negative |
| Stenotrophomonas maltophilia | Gram-negative | bacillus | negative |
Further Reading
- Microbe Online. Oxidase Test: Principle, Procedure and Oxidase-Positive Organisms.
