Question

29. a test could not effectively discriminate one microbe from another microbe as it normally should, which of the following would apply about that test? (see the Lab Manual). 2. inadequate sensitivity b. inadequate specificity 30. We will also be running the Methyl Red and Voges-Proskauer tests (Lab 5-3). The Methyl Red (MR) test is designed to detect microbes that produce which of the following? a. Mixed acids b. Stable acids c. Chemicals that reduce the pH to 4.4 or less d. All of the above 31. The Vogues-Proskauer (VP) test is designed to detect microbes that produce which of the following a. Acetoin b. 2,3 butanediol c. Chemicals that make the pH greater than 4.4 d. All of the above 32. What type of media is used in an MR-VP test? a. Agar plate b. Agar slant c. Agar deep d. Broth culture 33. How do you obtain results in an MR-VP test according to the lab manual? a incubate 24 hours and look for color changes in the media b. incubate 48 hours, split the sample, and look color changes after adding reagents (chemicals) c. incubate at least 5 days, look for color changes in the media d. none of the above 34. What color is produced in a positive MR test result? a. Yellow b. Red c. Copper d. Green 35. What color is produced in a positive VP test result? 1. Yellow b. Red c. Copper d. Green 36. The Catalase test (Lab Exercise 5-4) is what type of test? Utilization test b. Ability to respire c. Intracellular hydrolytic enzyme test d. Hydrolytic exoenzyme test

Answer 1

29) Option b ; inadequate specificity is the right answer.

A test when said sensitive implies if the particular growth of microbes is present or absent to find the type of strain or a specific microbe in the test.So inorder to distinguish between two or more microbes specificity is to be considered.

30) Methyl Red test uses the ability of a microbe to metabolize glucose to pyruvic acid and further to produce stable acids to mixed acids.This purely depends on the type of microbes involved in the test.So all acids produced by microbes may be identified.Therefore Option "d" is the correct answer.

31) Option d is correct.

Although VP test is used to detect acetoin in the broth produced by microbes;in some cases of fermentative pathway butanediol pathway is undertaken producing 2,3 butanediol or compounds of pH greater than 4..4

32) Option d is correct

Usually a broth containing the bacterial requirements are employed inorder to detect the color easily.

33) Option c is correct

Recent researches suggest incubation for 3-5 days in MR-VP test.

34) Option b is the correct answer

A stable red color is produced for a postive MR test which indicates the glucose was metabolized by the microbe into pyruvic acid.

35)Option b is the correct answer

A positive VP test produces a cherry red color.

36) Option c is the correct answer

Catalase test is an intracellular hydrolytic enzyme test which catalyzes decomposition of  hydrogen peroxide to water and carbon dioxide.