Answer : The possible explanation as to why this test identifies the presence of cytochrome c oxidase and not other oxidases (like E. coli)
is because an oxidase test mostly relies on a reagent that will allow to change colors only when it gets oxidized.
The reagent widely used in the test reacts specifically with cytochrome c oxidase by acting in place of oxygen to receive electrons from the cytochrome and
transfer of electrons takes place to
, which reduces it to water.