The reagents used in the oxidase test have been shown to auto-oxidize, so it is very important to use fresh reagents, no older than 1 week.
Both bacteria and yeast grown on media containing high concentrations of glucose show inhibited oxidase activity, so it is recommended to test colonies grown on media without excess sugar, such as nutrient agar. Tryptic soy agar is also an excellent media.
Bacteria grown on media containing dyes may give aberrant results.
The test reagents will effectively kill the microorganisms, so sub-culturing should be done prior to adding any reagent to an active culture.
The oxidase test can be used in the presumptive identification of Neisseria and in the differentiation and identification of gram-negative bacilli. Oxidase-positive organisms should be examined by gram stain to determine morphology and gram reaction. Additional biochemical tests are recommended for complete identification.
Use of a nichrome or other iron containing loop may yield false-positive reactions. Platinum loops are recommended.
Most Haemophilus are oxidase-positive. Less sensitive strips or reagents may yield false-negative results.
Oxidase reactions of gram-negative bacilli should be determined on non-selective and non-differential media to ensure valid results. Also, colonies taken from media containing high levels of glucose may give false-negative reactions.
It is recommended to use colonies that are 18-24 hours old. Older colonies will produce weaker reactions.
Any color changes appearing after 20 seconds should be disregarded.
The reagents used in the oxidase test have been shown to auto-oxidize, so it is very important to use fresh reagents, no older than 1 week.Both bacteria and yeast grown on media containing high concentrations of glucose show inhibited oxidase activity, so it is recommended to test colonies grown on media without excess sugar, such as nutrient agar. Tryptic soy agar is also an excellent media.Bacteria grown on media containing dyes may give aberrant results.The test reagents will effectively kill the microorganisms, so sub-culturing should be done prior to adding any reagent to an active culture.The oxidase test can be used in the presumptive identification of Neisseria and in the differentiation and identification of gram-negative bacilli. Oxidase-positive organisms should be examined by gram stain to determine morphology and gram reaction. Additional biochemical tests are recommended for complete identification.Use of a nichrome or other iron containing loop may yield false-positive reactions. Platinum loops are recommended.Most Haemophilus are oxidase-positive. Less sensitive strips or reagents may yield false-negative results.Oxidase reactions of gram-negative bacilli should be determined on non-selective and non-differential media to ensure valid results. Also, colonies taken from media containing high levels of glucose may give false-negative reactions.It is recommended to use colonies that are 18-24 hours old. Older colonies will produce weaker reactions.Any color changes appearing after 20 seconds should be disregarded.
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