The Non-Enteric Rods: Oxidase test
Another major characteristic that helps identify the Chart 5
organisms is the oxidase test. The oxidase test is a quick and simple 5 minute
test done directly from a bacterial colony on a blood agar plate. Some bacteria
possess a cytochrome oxidase system that facilitates the utilization of oxygen
as a final hydrogen acceptor in reducing molecular oxygen to hydrogen peroxide.
The oxidase strips or swabs contain various reagents which support a series of
reactions that lead to a final oxidase reaction and a purple color. Oxidase
negative organisms cause little or no color change.
The slide above shows an oxidase positive sample on the left and an oxidase
negative sample on the right.
ALL OF THE CHART 5 NON-ENTERIC RODS ARE OXIDASE POSITIVE. Some of the
positive reactions are weak, so don't hesitate to check with an instructor if
you are not sure.
