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☰ The oxidase test is a test to detect the enzyme cytochrome oxidase in Gram-negative bacteria which produce this enzyme, such as Neisseria or Pseudomonas.
☰ Oxidase Discs (OX) are absorbent paper discs impregnated with N, N, N ’, N’-Tetramethyl-p-phenylenediamine dihydrochloride. In the presence of cytochrome oxidase, N, N, N ’, N’-Tetramethyl-p-phenylenediamine dihydrochloride (colorless) forms a compound.
Oxidase test positive and negative (source : ASM MicrobiologyLibrary)
☰ Positive reaction : dark blue to purple coloration appearing within 30 seconds.
☰ Negative reaction : absence of coloration or coloration beyond 30 seconds.
Oxidase Positive Bacteria | Neisseria (toutes espèces) / Actinobacillus lignieresii / Aeromonas spp. / Actinobacillus equuli / Pasteurella spp. / Bordetella pertussis / Vibrio spp. / Bac. anthracis / Cordiobacterium hominis / Bac. subtillis / Pseudomonas spp. / Brucella spp. / Flavobacterium spp. / Chromobacterium spp. / Alcaligenes spp. / Eikenella corrodens / Moraxella spp. / Plesiomonas spp. / Campylobacter spp. / Branhamella catarrhalis / Micrococcus spp. |
Negative Oxidase Bacteria | Staphylococcus spp. / Pseudomonas mallei / Streptococcus spp. / Pseudomonas maltophilia / Gemella haemolysans / Bordetella parapertussis Peptococcus spp. / Actinobacillus / Peptostreptococcus spp. / actinomycetem-comitans / Leuconostoc spp. / Anaerobier (tous) / Corynebacterium spp. / Listeria spp. / Pasteurella haemolytica / Lactobacillus spp. / Bacillus spp. / Streptobacillus / Enterobacteriaceae / Mycoplasma spp. / Acholeplasma spp. |
☰ Variable oxidase : (positive or negative depending on the strain): Actinobacillus, Brucella, Haemophilus, Pasteurella.
Q : What does the oxidase test determine?
A : The oxidase test is a biochemical reaction that determines the presence or absence of cytochrome oxidase, it is one of the main bacterial identification tests.
Q : What color is a positive oxidase test?
A : Dark purple
Q : Does E coli test positive for oxidase?
A : Non, E coli test negative for oxidase, the entire family of Enterobacteriaceae are oxidase negative
Q : Why is it important to read oxidase results within 30 seconds?
A : In this test, the timing is important. The reagents of oxidase test is unstable, If it is exposed to air for too long , the oxygen will change the reagent color as time passes (spontaneously become oxidized
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