Ace your Selenite F Broth protocols with this 30-MCQ mock test! Covering composition, incubation, subculturing, and safety practices, this resource is essential for clinical microbiologists, food safety labs, and public health trainees. Includes detailed answer explanations, timed test strategies, and ISO/CLSI alignment. Perfect prep for ASCP, AMT exams, and lab competency audits.

How to Use This Mock Test :

1. Timed Simulation: Complete in 40 minutes.
2. Focus Areas:
– Sodium selenite as an inhibitory agent
– Incubation conditions (time/temperature)
– Subculturing techniques to solid media (e.g., XLD Agar)
– Safety handling (selenium toxicity)
3. Scoring: >24/30 = proficiency; review incorrect answers.

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Microbiology Department

Selenite F Broth MCQs Mock Test

Master Selenite F Broth with 50 FAQs & 30 MCQs! Learn selective enrichment principles for Salmonella/Shigella, safety handling (selenium toxicity), incubation protocols, and subculture techniques. Essential for clinical labs, food testing (ISO 6579), and microbiology exams.

Read Full Article: Selenite F Broth FAQs and MCQs

1 / 30

Category: Clinical Laboratory

Which ingredient maintains pH in Selenite Broth?

Sodium selenite

Casein hydrolysate

Sodium phosphate

Lactose

2 / 30

Category: Clinical Laboratory

Dehydrated Selenite Broth powder should be stored:

With desiccants

At 10–30°C in a dry place

In sunlight

Frozen

3 / 30

Category: Clinical Laboratory

Lactose in Selenite Broth serves to:

Provide fermentable carbohydrates

Both b and c

Act as a buffer

Inhibit Gram-positive bacteria

4 / 30

Category: Clinical Laboratory

Which supplement may improve Salmonella recovery?

L-cystine

Hemin

Vitamin K

Sucrose

5 / 30

Category: Clinical Laboratory

Sodium selenite primarily inhibits:

Mycobacterium

 E. coli and fecal streptococci

 Pseudomonas

Salmonella

6 / 30

Category: Clinical Laboratory

After incubation, subculture should be done on:

Sabouraud dextrose agar

MacConkey or XLD agar

Blood agar

Chocolate agar

7 / 30

Category: Clinical Laboratory

How much stool sample should be added to Selenite Broth?

10 g

1–2 g

5 g

0.1 g

8 / 30

Category: Clinical Laboratory

What is the primary purpose of Selenite F Broth?

Detect viruses

Isolate E. coli

Enrich Salmonella and Shigella

Culture Staphylococcus

9 / 30

Category: Clinical Laboratory

Selenite Broth can preserve Vibrio cholerae for:

24 hours

1 week

1 hour

2–5 days

10 / 30

Category: Clinical Laboratory

What is the final pH of Selenite F Broth?

6.0 ± 0.2

5.2 ± 0.2

8.5 ± 0.2

7.0 ± 0.2

11 / 30

Category: Clinical Laboratory

The inhibitory effect of selenite diminishes after:

6–12 hours

1 hour

24–48 hours

1 week

12 / 30

Category: Clinical Laboratory

The “F” in Selenite F Broth stands for:

Fecal

Leifson’s modified formula

Fermentative

Fast-growing

13 / 30

Category: Clinical Laboratory

Which component makes Selenite Broth selective?

Sodium selenite

Lactose

Casein hydrolysate

Sodium phosphate

14 / 30

Category: Clinical Laboratory

What should you do if a red precipitate forms in the broth?

Discard the medium

Autoclave again

Shake vigorously

Add more lactose

15 / 30

Category: Clinical Laboratory

How is Selenite Broth sterilized?

Filtration

Boiling water bath for 10 minutes

Autoclaving at 121°C

Dry heat sterilization

16 / 30

Category: Clinical Laboratory

The recommended depth of broth in tubes is:

1 cm

10 cm

3 cm

5 cm

17 / 30

Category: Clinical Laboratory

What indicates microbial growth in Selenite Broth?

Turbidity

Color change to pink

Formation of gas bubbles

Red precipitate

18 / 30

Category: Clinical Laboratory

On MacConkey Agar, Salmonella appears as:

Colorless colonies

Pink colonies

Green colonies

Black colonies

19 / 30

Category: Clinical Laboratory

If coliforms overgrow in Selenite Broth, the likely cause is:

Too much lactose

Autoclaving the broth

Incubation >24 hours

Incubation <12 hours

20 / 30

Category: Clinical Laboratory

Why should Selenite Broth NOT be autoclaved?

Lactose caramelizes

Heat destroys selenite’s inhibitory properties

It becomes too selective

Casein precipitates

21 / 30

Category: Clinical Laboratory

Selenite F Broth is NOT recommended for:

Stool samples

Urine samples

Blood cultures

Food samples

22 / 30

Category: Clinical Laboratory

Selenite Broth must be stored at:

–20°C

2–8°C

37°C

25–30°C

23 / 30

Category: Clinical Laboratory

Which bacteria are naturally resistant to selenite?

Streptococcus

E. coli

Clostridium

Proteus and Pseudomonas

24 / 30

Category: Clinical Laboratory

Which organization recommends Selenite Broth for food testing?

APHA

WHO

CDC

FDA

25 / 30

Category: Clinical Laboratory

Sodium selenite is hazardous because it is:

Corrosive and teratogenic

Flammable

Radioactive

Explosive

26 / 30

Category: Clinical Laboratory

For urine samples, Selenite Broth should be:

Mixed 1:1 with urine

Avoided

Autoclaved first

Used at double strength

27 / 30

Category: Clinical Laboratory

Who developed Selenite Broth?

Louis Pasteur

Joseph Lister

Robert Koch

Leifson

28 / 30

Category: Clinical Laboratory

Selenite Broth should NOT be used as the sole medium because:

It lacks nutrients

It may miss low-pathogen loads

It is too expensive

It inhibits Salmonella

29 / 30

Category: Clinical Laboratory

Optimal incubation time for Selenite Broth is:

6 hours

72 hours

48 hours

12–24 hours

30 / 30

Category: Clinical Laboratory

Quality control for Selenite Broth includes testing with:

 E. coli (ATCC 25922)

Both a and b

Salmonella Typhimurium (ATCC 14028)

Candida albicans

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Key Topics Covered

Composition: Peptone, lactose, sodium selenite.
Mechanism: Selenite disrupts cellular respiration in non-target bacteria.
Protocols: 1:10 sample-to-broth ratio, 37°C incubation, subculture to selective agars.
Limitations: Not for *Shigella*; short shelf-life; toxic to lab personnel.
Applications: Stool cultures, food testing (ISO 6579), outbreak investigations.

Pro Tip:
Always pair Selenite F Broth with a secondary selective agar (e.g., Hektoen or SS Agar) for optimal *Salmonella* recovery. Handle under fume hoods due to selenium volatility!

Possible References Used

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