Oxidase test: Difference between revisions

Revision as of 17:33, 29 October 2019

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
All oxidase-positive bacteria are aerobic
- P: Pseudomonas spp.
- V: Vibrio cholerae
- N: Neisseria spp.
- C: Campylobacter spp.
- H: Helicobacter spp. / Haemophilus spp.
- Aeromonas spp.

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+* Identifies '''cytochrome C oxidase''' by testing for the ability to oxidize tetramethyl-p-phenylenediamine to indophenols, which are purple
-Source: [https://microbeonline.com/oxidase-test-principle-procedure-and-oxidase-positive-organisms/ microbonline.com]
+* The test is positive when it turns '''purple''' within 10 seconds
+** Must be done from plain 5% SBA
+* All oxidase-positive bacteria are aerobic
+** '''P''': ''Pseudomonas'' spp.
+** '''V''': ''Vibrio cholerae''
+** '''N''': [https://microbeonline.com/neisseria-gonorrhoeae-properties-disease-pathogenesis-and-laboratory-diagnosis/ ''Neisseria''] spp.
+** '''C''': ''Campylobacter'' spp.
+** '''H''': ''Helicobacter'' spp. / ''Haemophilus'' spp.
+** ''Aeromonas'' spp.
+== Further Reading ==
-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.
+* Microbe Online. [https://microbeonline.com/oxidase-test-principle-procedure-and-oxidase-positive-organisms/ Oxidase Test: Principle, Procedure and Oxidase-Positive Organisms].
-[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]]]
-'''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.
-'''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.
-== Procedure ==
-# Take a filter paper soaked with the substrate tetramethyl-p-phenylenediamine dihydrochloride
-# Moisten the paper with a sterile distilled water
-# Pick the colony to be tested with wooden or platinum loop and smear in the filter paper
-# Observe inoculated area of paper for a color change to deep blue or purple within 10-30 seconds
-=== Precautions ===
-# 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
-# Interpret the results within 10 seconds, timing is critical
-# 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.
-# 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.
-== Interpretation ==
-# '''Positive:''' Development of '''dark purple color''' (indophenols) within 10 seconds
-# '''Negative:''' Absence of color
-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.'''
-'''Name of Oxidase positive bacteria are:''' '''PVNCH'''
-# '''P''': ''Pseudomonas'' spp.
-# '''V''': ''Vibrio cholerae''
-# '''N''': [https://microbeonline.com/neisseria-gonorrhoeae-properties-disease-pathogenesis-and-laboratory-diagnosis/ ''Neisseria''] spp.
-# '''C''': ''Campylobacter'' spp.
-# '''H''': ''Helicobacter'' spp. / ''Haemophilus'' spp.
-# ''Aeromonas'' spp.
-# Alcaligens
 [[Category:Diagnostics]]