Oxidase Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Oxidase and links to relevant pages within the course.
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| Glucose Test The test for glucose is a double sequential enzyme reaction, utilizing the glucose-oxidase/peroxidase method. In the first reaction, glucose oxidase catalyzes the oxidation of glucose to gluconic acid and hydrogen peroxide. Then, the peroxidase catalyzes the oxidation of a chromogen by the hydrogen peroxide to form a colored product. This method does not react with lactose, fructose or galactose. Study the dipstick color chart to become familiar with the range of color changes. The urine specimen should be at room temperature for these enzyme reactions to occur properly. | View Page |
| Which one of the following statements about acetominophen metabolism is false? | View Page |
| Most common methods for measuring bilirubin are based on the reaction of bilirubin with: | View Page |
| A chemical reaction that is utilized by many different analytical methods involves: | View Page |
| The oxidase test is used to presumptively identify: | View Page |
| Different species of Neisseria can be differentiated from each other by: | View Page |
| Which of the following is not true about members of the Enterobacteriaceae: | View Page |
| Alternate Tests for Sugars There are two basic types of tests that are used to screen or monitor glycosuria -- copper reduction tests and enzyme tests. Most enzyme tests use the enzyme glucose oxidase impregnated on a dipstick along with a chromagen, and are specific for detecting only glucose. The copper reduction tests, however, detect any reducing substance. Clinitest® uses the classic Benedict’s copper reduction reaction. Any reducing substances present in the urine will react with the copper sulfate reagent, and the blue cupric sulfate is subsequently reduced to cuprous oxide. The resultant color change from blue through green to orange is proportional to the amount of reducing substance in the urine sample. | View Page |
| A 25 year-old female presented in the emergency room with an acute urethral discharge of 2 days duration. A smear for gram stain was obtained (see accompanying image). Many polymorphonuclear leukocytes and intracellular and extracellular gram negative diplococci were observed.
Based on the clinical history and the gram stain observation, a diagnosis of gonorrhea can be made. | View Page |
| The positive oxidase reaction as shown in the photograph (yellow arrow) rules out the following two look-alike organisms of N. gonorrhoeae: | View Page |
| The carbohydrate utilization reaction seen in the QuadFerm system shown in the picture provides a definitive identification of N. gonorrhoeae: | View Page |
| Eikenella - catalase & oxidase Eikenella corrodens (E) belongs to the HACEK group of miscellaneous gram-negative bacilli which includes Haemophilus aphrophilus (H), Actinobacillus actinomycetemcometans (A), Cardiobacterium hominis (C) and Kingella kingae (K).Cytochrome oxidase and catalase are two rapid tests that help separate the several members of this group.Eikenella corrodens shows cytochrome oxidase activity, but not catalase activity.
The positive oxidase reaction separates E. corrodens from Haemophilus aphrophilus and Actinobacillus actinomycetemcomitans, which are both negative.A. actinomycetemcomitans is also catalase positive, an additional characteristic separating it from E. corrodens, which is negative.As Kingella kingae is also oxidase positive and catalase negative, other tests are needed for differentiation. K. kingae produces acid from glucose and maltose (E. corrodens is asaccharolytic). | View Page |
| A bacterial isolate that produces pitting of the agar and has a bleach-like odor is probably E. corrodens. Closely related species that must be ruled out include: | View Page |