MCQs on biochemical tests reaction of Enterobacteriaceae family (gram negative bacteria)

    MCQs on biochemical tests reaction of Enterobacteriaceae family (gram negative bacteria) 

1.Which biochemical test assesses the ability of bacteria to ferment lactose, sucrose, and glucose, as
well as produce gas and hydrogen sulfide?
a) Indole Test
b) Methyl Red Test
c) Voges-Proskauer Test
d) Triple Sugar Iron Agar (TSI) Test

2.The production of red color after the addition of the MR indicator indicates a positive result for
which of the following test?
a) Citrate Utilization Test
b) Indole Test
c) Methyl Red Test
d) Urease Test

3.Which of the following is a non lactose fermenter gram negative bacteria?
a) Escherichia coli
b) Enterobacter aerogenes
c) Klebsiella pneumoniae
d) Salmonella typhi     

4. Blackening of the medium in the Sulfur Indole Motility (SIM) Test indicates:
a) Citrate utilization
b) Hydrogen sulfide (H2S) production
c) Indole production
d) Motility

5.The ability of bacteria to hydrolyze urea to produce ammonia and carbon dioxide is assessed by which test?
a) Indole Test
b) Sulfur Indole Motility (SIM) Test
c) Urease Test
d) Voges-Proskauer Test

6. Which of the following agar medium is generally used for the motility test? ?
a) Semisolid agar medium or Sulfur Indole Motility agar
b) Liquid broth medium
c) Solid agar medium
d) Triple Sugar Iron Agar (TSI) Test

7. What is the positive result for the bacterial growth on Simmon's citrate agar slant ?
a) The agar media color remains green color
b) The agar media color changes from its original green color to blue
c) The agar media color changes to black
d) None of the above

8. Which of the following refers to Voges-Proskauer (VP) Test for bacterial cultures? 

a) Indole production from the amino acid tryptophan
b) Hydrogen sulfide (H2S) production
c) Production of ammonia and carbon dioxide from urea hydrolyze
d) Production of acetoin from glucose fermentation

9. Proteus vulgaris is one of the few gram negative bacteria that can ferment sucrose. Which of the following refers to the positive result for sucrose test?
a) Decrease in pH of the medium and color changes from red to yellow
b) Increase in pH of the medium and color changes from red to yellow
c) pH of the medium remains same, red color
d) None of the above

10. Which of the following is not a common biochemical reaction used for the differentiation of Enterobacteriaceae?
a) Citrate utilization
b) Heme production
c) Indole production
d) Lactose fermentation
e) Motility test
f) Urea hydrolysis

11. Which of the following Enterobacteriaceae have swarming (highly motile) motility after growth in semi solid agar tube?
a) Klebsiella pneumoniae
b) Proteus vulgaris
c) Staphylococcus aureus
d) Shigella sonnei

Answers:
1. d) Triple Sugar Iron Agar (TSI) Test

TSI is used to assess the fermentation of sugars (glucose, lactose, and sucrose) and production of gas and hydrogen sulfide. Color changes and gas production patterns help identify bacterial species.

2. c) Methyl Red Test. The MR test detects the production of stable acids from glucose fermentation. 

3. d) Salmonella typhi. It is a non lactose fermenter, Salmonella spp do not produce acid from lactose fermentation when grown on MacConkey agar. The colonies of non-lactose-fermenting bacteria remain their natural color, which is often colorless, this is helpful for distinguishing Salmonella from lactose-fermenting (pink colonies) Enterobacteriaceae

4. b) Hydrogen sulfide (H2S) production. The SIM test evaluates sulfur reduction, indole production, and bacterial motility. Blackening of the medium indicates hydrogen sulfide production.

5. c) Urease Test. This test evaluates the ability of bacteria to hydrolyze urea to produce ammonia and carbon dioxide, positive results are indicated by a color change in the medium from yellow to pink.

6. a) Semisolid agar medium or Sulfur Indole Motility agar. Lower concentration of agar in semisolid agar medium than solid agar media thus allowing bacteria to move more easily.

7. b) The agar  media color changes from its original green color to blue.

Bacteria that can utilize citrate as a carbon source produce citrase. In citrate positive test, the medium changes from its original green color to blue.

8. d) Production of acetoin from glucose fermentation. 

The VP test determines the production of acetoin from glucose fermentation. Positive results are indicated by a red color after the addition of specific reagents.

9. a) Decrease in pH of the medium and color changes from red to yellow. The medium will turn yellow due to the accumulation of acids as a result of  sucrose fermentation.

10. b) Heme production. Heme production is not commonly used as a test for differentiating Enterobacteriaceae. It is a molecule that is involved in oxygen transport and is a component of hemoglobin, a protein found in red blood cells.

11. b) Proteus vulgaris. The bacteria shows diffuse growth pattern and spread outward from the point of inoculation inside the agar tube.

a) Klebsiella pneumoniae, c) Staphylococcus aureus, and d) Shigella sonnei are non-motile bacteria and will remain localized at the point of inoculation inside the agar tube.