Oxidase test

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The oxidase test is a simple and fast biochemical method for the detection of the enzyme cytochrome c oxidase in the respiratory chain of cells . The oxidase test is used for the classification of bacteria ( Bunte series ) and in histology . The oxidase reagent reduces the cytochrome c oxidase via cytochrome c . In this case, the colorless reagent becomes an intensely colored radical - cation oxidized (Wurster cation).

The oxidase test is specific for cytochrome c oxidases. Quinol oxidases do not react here.

Oxidase reagents

There are three different oxidase reagents:

Kovacs reagent

The Kovacs reagent is a solution of 10 mg / ml N , N , N ', N ' -tetramethyl-1,4-phenylenediamine (TMPD) in 100 mM phosphate buffer (pH 7). A bacterium is oxidase-positive if the cells turn into an intense blue color (Wurster blue) within one minute of adding the reagent. If there is no reaction or if it reacts later, the bacterium is oxidase negative.

Gordon-McLeod reagent

The Gordon-McLeod reagent is a solution of 10 mg / ml N , N- dimethyl-1,4-phenylenediamine (DMPD) in 100 mM phosphate buffer (pH 7). A bacterium is oxidase-positive if the cells turn into an intense red color (Wurster red) within one minute of adding the reagent. If there is no reaction or if it reacts later, the bacterium is oxidase negative.

NADI reagent

The NADI reagent (according to Ehrlich ) is a mixture of equal parts by volume of 50 mM α-naphthol solution in 50% by volume of ethanol and 10 mg / ml of N , N- dimethyl-1,4-phenylenediamine solution (DMPD) in 100 mM phosphate buffer (pH 7). A bacterium is oxidase-positive if the cells turn into an intense blue color ( indophenol blue ) within one minute . If there is no reaction or if it reacts later, the bacterium is oxidase negative.

literature

  1. ↑ N. Kovacs (1956): Identification of Pseudomonas pyocyanea by the oxidase reaction. In: Nature. Vol. 178, p. 703. PMID 13369512 doi : 10.1038 / 178703a0
  2. ↑ JC Gordon & JW McLeod (1928): The practical application of the direct oxidase reaction in bacteriology. In: J. Path. Bact. Vol. 31, p. 185.
  3. ^ CM Carpenter et al. (1947): The oxalate salt of p-aminodimethylaniline, an improved reagent for the oxidase test. In: Science. Vol. 105, pp. 649-650. doi : 10.1126 / science.105.2738.649
  4. ^ WL Gaby & C. Hadley (1957): Practical laboratory test for the identification of Pseudomonas aeruginosa. In: J. Bacteriology. Vol. 74, pp. 356-358. PMID 13475249 , PMC 314647 (free full text).
  5. ↑ P. Ehrlich (1885): The organism's need for oxygen. A color analytical study. Habilitation thesis, University of Berlin.