The IMVIC Tests (F)

Question 1

What is the meaning of IMViC?

Answer 1

Indole, Methyl red, Voges-Proskauer, and Citrate utilization test

Question 2

What is the purpose of IMViC tests?

Answer 2

These tests are routinely done in the microbiology lab for presumptive identification of microorganisms mostly belong to the Enterobacteriaceae and other related spp

Question 3

What is the principle of rxn for indole production?

Answer 3

Tryptophan + Water (via the action of tryptophanase) -> Indole + Pyruvate + Ammonium

Question 4

What is indole?

Answer 4

It is one of the degradation products from the metabolism of AA tryptophan

Question 5

What is the action brought by the bacteria w/ the tryptophanase?

Answer 5

It can cleave tryptophan thus producing indole, pyruvic acid, and ammonia

Question 6

Where and how are indole, pyruvic acid, and ammonia detected?

Answer 6

These can be detected in tryptophan test medium by observing the development of a red color after adding the solution containing p-dimethylaminobenzaldehyde

Question 7

What are the results in indole production test?

Answer 7

Indole (+)

Indole (-)

Question 8

What is the purpose of methyl red test?

Answer 8

This test detects the production of sufficient acid during fermentation of glucose by bacteria and sustained maintenance of a pH below 4.5

Question 9

What is the procedure (or steps) in methyl red test?

Answer 9

1) The test organism is inoculated in glucose phosphate broth and inoculated at 37 DC for 2 - 5 days
2) Then add 5 drops of 0.04% solution of methyl red
3) Mix well
4) Read the results immediately

Question 10

What are the results in methyl red test?

Answer 10

Methyl red (+)
Methyl red (-)

Question 11

What is the purpose of Voges-Proskauer test?

Answer 11

It is used to detect the formation of acetylmethylcarbinol (acetoin) as a product of glucose fermentation

Question 12

What is acetoin?

Answer 12

It is formed as a product of an alternate pathway of glucose fermentation utilized by some spp of Enterobacteriaceae

Question 13

What are the 2 test rgnts used in Voges-Proskauer test?

Answer 13

1) 40% KOH

2) Alpha-naphtol

Question 14

What are done to the 2 test rgnts (in Voges-Proskauer test)?

Answer 14

These are added to the test broth after 48 hrs incubation and exposed to atmospheric oxygen

Question 15

What is the meaning of VP test?

Answer 15

Voges-Proskauer test

Question 16

What are the results in VP test?

Answer 16

VP (+)

VP (-)

Question 17

What is the purpose of citrate utilization test?

Answer 17

To determine if a bacterium can utilize citrate as a sole source of carbon for metabolism and growth

Question 18

Production of blue color in the test medium (in citrate utilization test) indicates what?

Answer 18

It indicates the presence of alkaline products

Question 19

What is the procedure (or steps) in citrate utilization test?

Answer 19

1) Streak the slant back and forth w/ a light inoculum from isolated colony
2) Incubate aerobically at 35 - 37 DC for overnight

Question 20

What are the results in citrate utilization test?

Answer 20

(-)

+

Question 21

What are the IMViC rxns of Escherichia coli?

Answer 21

I: (+)
M: (+)
Vi: (-)
C: (-)

Question 22

What are the IMViC rxns of Edwardsiella tarda?

Answer 22

I: (+)
M: (+)
Vi: (-)
C: (-)

Question 23

What are the IMViC rxns of Proteus vulgaris?

Answer 23

I: (+)
M: (+)
Vi: (-)
C: (-)

Question 24

What are the IMViC rxns of Klebsiella pneumoniae?

Answer 24

I: (-)
M: (-)
Vi: (+)
C: (+)

Question 25

What are the IMViC rxns of Klebsiella oxytoca?

Answer 25

I: (+)
M: (-)
Vi: (+)
C: (+)

Question 26

What are the IMViC rxns of Enterobacter spp.?

Answer 26

I: (-)
M: (-)
Vi: (+)
C: (+)

Question 27

What are the IMViC rxns of Serratia marcescens?

Answer 27

I: (-)
M: (-)
Vi: (+)
C: (+)

Question 28

What are the IMViC rxns of Citrobacter freundii?

Answer 28

I: (-)
M: (+)
Vi: (-)
C: (+)

Question 29

What are the IMViC rxns of Citrobacter koseri?

Answer 29

I: (+)
M: (+)
Vi: (-)
C: (+)