The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases.[1] It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) or N,N-Dimethyl-p-phenylenediamine (DMPD), which is also a redox indicator. The reagent is a dark blue to maroon color when oxidized, and colorless when reduced.
Contents |
Classification
Strains may either be oxidase positive (OX+) or negative (OX-).
OX+
OX+ normally means that the bacterium contains cytochrome c oxidase and can therefore utilize oxygen for energy production with an electron transfer chain.
Typically the Pseudomonadaceae are OX+
Another example is the preliminary identification of Neisseria and Moraxella genera, which are both oxidase positive, Gram-negative diplococci.
OX-
Typically Enterobacteriaceae are OX-.[2]
Procedures
- Wet each disk with about 4 inoculating loops of de-ionized water.
- Use a loop to aseptically transfer a large mass of pure bacteria to the disk.
- Observe the disk for up to 3 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.
Alternatively, 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 media, two-to-three drops of the reagent DMPD is added to the surface of each organism to be tested.
- A positive test (OX+) will result in a color change to pink, through maroon and into black, within 10–30 seconds.
- A negative test (OX-) will result in a light pink coloration or absence of coloration.
References
- ^ "Oxidase Test and Modified Oxidase Test". http://web.mst.edu/~microbio/Lab_Supplement/Oxidase.html. Retrieved 2008-11-07.
- ^ 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. PMID 7240403. PMC: 273917. http://jcm.asm.org/cgi/pmidlookup?view=long&pmid=7240403.
External links
- Oxidase test video
- Oxidase Test Procedure
 |
This bacteria-related article is a stub. You can help Wikipedia by expanding it. |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
