CLINICAL MICROBIOLOGY

BIOCHEMICAL TESTS( Cont..)

2)  Oxidase Test:  The oxidase test is a means of specifically detecting the presence of the terminal enzyme system in aerobic respiration called Cytochrome C oxidase.  The aerobic respiratory mechanism is composed of a number of enzymes which alternately oxidize & reduce each other by donating or accepting electrons derived from hydrogen. Hydrogen atoms are removed from various substrate compounds during oxidation reaction & ultimately the hydrogen atoms are combined with oxygen to form water. Thus, cytochrome C oxidase is the terminal or last hydrogen electron acceptor in this chain, its function being to transfer the hydrogen electrons to oxygen to form water molecules. This is the classic aerobic respiration scheme that most microorganisms utilize to derive energy from the food they take in as molecules of ATP.
               The ability of an organism to produce cytochrome C oxidase can be determined by using the reagent tetramethyl-p-phenylenediamine. This reagent serves as an artifical substrate donating electrons & thereby becoming oxidized to blackish compound in the presence of the enzyme oxidase & free oxygen. 
The members of Enterobacteriaceae give negative result whereas  Pseudomonas spp, Aeromonas spp, Vibrio spp, Neisseria spp, etc give positive result. 

                                         Fig: Oxidase Test 
    Please visit these links: 
        en.wikipedia.org/wiki/Oxidase_test
       www.vumicro.com › Home › Reference Books › Biochemical Tests
      www.microbelibrary.org/index.php/library/...test/3287-oxidase-test
       www.austincc.edu/microbugz/oxidase_test.php
       www.youtube.com/watch?v=z1HsdAQO7m4
       www.youtube.com/watch?v=7Aa1xO2cC1M
       www.bd.com/ds/productCenter/231746.asp

Cited By Kamal Singh Khadka 
Assistant Professor In Pokhara University, Regional college of Science & Technology, PNC, NA

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