Oxidase test

Oxidase test

The oxidase test is a test used in catalase).[3]


  • Classification 1
    • OX+ 1.1
    • OX- 1.2
  • Procedures 2
  • References 3
  • External links 4


Strains may be either oxidase-positive (OX+) or oxidase-negative (OX-).


OX+ normally means the bacterium contains cytochrome c oxidase and can therefore use oxygen for energy production by converting O2 to H2O2 or H2O with an electron transfer chain.

The Pseudomonadaceae are typically OX+

The Gram-negative diplococci Neisseria and Moraxella are oxidase-positive.

Many Gram-negative, spiral curved rods are also oxidase-positive, which includes Helicobacter pylori, Vibrio cholerae, and Campylobacter jejuni.

Also Legionella pneumophila is oxidase-positive.


OX- normally means the bacterium does not contain cytochrome c oxidase and, therefore, either cannot use oxygen for energy production with an electron transfer chain or employs a different cytochrome for transferring electrons to oxygen.

Enterobacteriaceae are typically OX-.[4]


  1. Wet each disk with about four inoculating loops of deionized water.
  2. Use a loop to aseptically transfer a large mass of pure bacteria to the disk.
  3. Observe the disk for up to three minutes. If the area of inoculation turns dark-blue to maroon to almost black, then the result is positive. If a color change does not occur within three minutes, the result is negative.

In alternative manner, live bacteria cultivated on trypticase soy agar plates may be prepared using sterile technique with a single-line streak inoculation. The inoculated plates are incubated at 37 °C for 24–48 hours to establish colonies. Fresh bacterial preparations should be used. After colonies have grown on the medium, 2-3 drops of the reagent DMPD are added to the surface of each organism to be tested.

  • A positive test (OX+) will result in a color change violet to purple, within 10–30 seconds.
  • A negative test (OX-) will result in a light-pink or absence of coloration.


  1. ^ "Oxidase Test and Modified Oxidase Test". Retrieved 2008-11-07. 
  2. ^ . Isenberg HD, editor. Clinical Microbiology Procedures Handbook. American Society for Microbiology; 2004. p. 3.3.2-
  3. ^ MacFaddin JF, editor. Biochemical Tests for Identification of Medical Bacteria. 3rd ed. Philadelphia:Lippincott Williams and Wilkins; 2000. p. 363-7
  4. ^ Farmer JJ, Fanning GR, Huntley-Carter GP, et al. (May 1981). "Kluyvera, a new (redefined) genus in the family Enterobacteriaceae: identification of Kluyvera ascorbata sp. nov. and Kluyvera cryocrescens sp. nov. in clinical specimens". J. Clin. Microbiol. 13 (5): 919–33.  

External links

  • Oxidase test video
  • Oxidase Test Procedure