Oxidase enzymes (e.g. cytochrome oxidase) are important (as electron transporters) to aerobes, facultative anaerobes, and microaerophiles in aerobic respiration. The oxidase test helps to differentiate between generas Neisseria and Pseudomonas (both of which are oxidase-positive) and Enterobacteriaceae (oxidase-negative).
After inoculation and incubation for 12-48 hours, 2-3 drops of reagent p-aminodimethylaniline oxalate is added to the medium. If the medium turns pink, then maroon, and then dark purple, the test is positive for cytochrome oxidase production. If there is no color change, the test is negative.
Clinical significance. The oxidase test helps to differentiate between generas Neisseria and Pseudomonas (both of which are oxidase-positive) and Enterobacteriaceae (oxidase-negative). The oxidase test helps to identify Neisseria meningitis, and also separate yeast Candida from Saccharomyces and Torulopsis.
Reference
Cappuccino, J. G., & Welsh, C. (2018). Microbiology: A laboratory manual.
