The
oxidase test is used to determine if an organism possesses the cytochrome
oxidase enzyme. The test is used as an aid for the differentiation of Neisseria, Moraxella, Campylobacter and Pasteurella species (oxidase positive).
It is also used to differentiate pseudomonads from related species.
Oxidase
positive bacteria possess cytochrome oxidase or indophenol oxidase (an iron
containing haemoprotein). Both of these catalyse the transport of electrons
from donor compounds (NADH) to electron acceptors (usually oxygen).
The
test reagent, N, N, N’, N’-tetramethyl-p-phenylenediamine dihydrochloride acts
as an artificial electron acceptor for the enzyme oxidase. The oxidised reagent
forms the coloured compound indophenol blue.
The
cytochrome system is usually only present in aerobic organisms which are
capable of utilising oxygen as the final hydrogen receptor. The end product of
this metabolism is either water or hydrogen peroxide (broken down by catalase).
There
are many method variations to the oxidase test. These include, but are not
limited to, the filter paper test, direct plate method, swab method,
impregnated oxidase test strip method and test tube method. All times and
concentrations are based upon the original recommendations.
Positive
Result
Development
of a deep purple-blue/blue colour indicates oxidase production.
Negative
Result
No
purple-blue colour/No colour change.
In
relation to the oxidase test, Public Health England has issued a technical
report, including safety information. The report can be accessed here.
Posted by Tim Sandle
No comments:
Post a Comment
Pharmaceutical Microbiology Resources