Cytochrome oxidase is an enzyme in aerobic respiration with hydrogen and oxygen used to form water. It is a hemoprotein with iron.
Organisms negative cytochrome oxidase:
(1) Enterobacteriaceae
(2) obligate anaerobes
Many other organisms produce oxide.
Reagents used for detection:
(1) Kovac's reagent (tetramethyl-p-phenylenediamine dihydrochloride)
(2) Gordon and MacLeod's reagent (dimethyl-phenylenediamine dihydrochloride)
Reagent may be added to agar media or applied to a colony by filter paper.
The reagents are colorless until they receive electrons via cytochrome oxidase. A positive reaction is a deep blue color that appears quickly.
Causes of a false positive reaction:
(1) stainless steel or nichrome wire inoculation loops (after flame sterilization)
(2) mixed isolate
Causes of a false negative reaction:
(1) breakdown of the reagent
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Specialty: Clinical Laboratory, Infectious Diseases
