What is the procedure of oxidase test?
What is the procedure of oxidase test?
Use the dropper to add a drop of oxidase reagent to the bacteria on the filter paper, and look for the appearance of blue or purple spots – a positive result. After 15 seconds, if no color appears, the test is negative for the presence of cytochrome oxidase.
What reagent is used in oxidase test?
tetra-methyl- p-phenylenediamine dihydrochloride
The oxidase test often uses a reagent, tetra-methyl- p-phenylenediamine dihydrochloride, as an artificial electron donor for cytochrome c. When the reagent is oxidized by cytochrome c, it changes from colorless to a dark blue or purple compound, indophenol blue.
How do you use an oxidase test disk?
Oxidase reaction is carried out by touching and spreading a well isolated colony on the oxidase disc. The reaction is observed within 5-10 seconds at 25-30°C. A change later than 10 seconds or no change at all is considered negative reaction.
What is the substrate for the oxidase test?
The active substrate in oxidase reagent, N,N,N,N- tetramethyl-p-phenylenediamine dihydrochloride, acts as an artificial electron acceptor for the enzyme oxidase and is oxidized to form the colored compound Wurster’s blue. Wurster’s blue is a purple compound that is readily visible and signifies a positive reaction.
Why do we use oxidase test?
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.
Why is the oxidase test useful?
Why does the oxidase test have to be read quickly?
Read the reaction within 20 seconds (NOT after), usually it will change in less than 15 seconds. The oxygen will change the reagent color as time passes, so it must be read quickly.
What are the precautions in oxidase test?
Do not use wire loop to transfer the culture as oxidase reagent may reacts with iron or nichrome to give false result
What is the principle of the oxidase test?
The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. When present, the cytochrome c oxidase oxidizes the reagent (tetramethyl-p-phenylenediamine) to (indophenols) purple color end product. When the enzyme is not present, the reagent remains reduced and is colorless.
Does E. coli test positive for oxidase?
The test result of the oxidase test for E. coli was negative and matched the expected result (Holt 179). The bacteria of the Genus Escherichia are facultative anaerobes. They can use aerobic respiration or fermentation metabolic pathways. The test result of the oxidase test for P. aeruginosa was not as expected.
Which bacteria are oxidase positive?
The oxidase test helps in identifying bacteria producing cytochrome c oxidase . It is a particular type of enzyme of the bacterial electron transport chain. Oxidase positive bacteria are classified as aerobic (uses oxygen as electron acceptor in respiration). On the other hand, oxidase negative bacteria can be anaerobic, facultative, or even aerobic.
