Hektoen Enteric Agar 30 MCQs Mock Test:

Welcome to the Hektoen Enteric (HE) Agar Mock Test, designed for students, laboratory professionals, and microbiology enthusiasts who want to evaluate their understanding of this important selective and differential culture medium.

Hektoen Enteric Agar is primarily used for the isolation of intestinal pathogens, especially Salmonella and Shigella species, from clinical specimens such as stool samples. Its selective agents inhibit unwanted Gram-positive organisms, while its differential components allow identification based on carbohydrate fermentation and hydrogen sulfide production.

This mock test contains 30 carefully structured questions that reflect real laboratory and examination scenarios. It is an excellent tool for assessing theoretical knowledge and practical understanding of enteric pathogen identification using HE Agar.

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Hektoen Enteric Agar MCQs Mock Test

Please read before starting the Martin Lewis Agar – 30 MCQs Mock Test. This test includes 30 multiple-choice questions, each with one correct answer. There is no negative marking, so attempt all questions. Avoid refreshing or closing the page to prevent losing your progress. After answering all questions, you may review your responses before submitting. If you want a Certificate, enter your correct Full Name and active Email after completing the test and before submission. Your certificate can be downloaded directly from the result page once the test is submitted.

Read Full Article: Hektoen Enteric Agar 50 FAQs and 30 MCQs

1 / 30

Category: Clinical Laboratory

Who developed HE Agar?

Louis Pasteur

Sylvia King and William Metzger

Alfred MacConkey

Robert Koch

2 / 30

Category: Clinical Laboratory

Which ingredient in HE Agar detects H₂S production?

Bromothymol blue

Bile salts

Lactose

Ferric ammonium citrate

3 / 30

Category: Clinical Laboratory

What is the role of peptones in HE Agar?

Offset bile salt inhibition

Inhibit gram-positive bacteria

Enhance lactose fermentation

Detect H₂S

4 / 30

Category: Clinical Laboratory

Which historical medium used brilliant green dye for selectivity?

Brilliant Green Agar

XLD Agar

Salmonella-Shigella Agar

EMB Agar

5 / 30

Category: Clinical Laboratory

The pH of HE Agar is:

5.5

6.5

8.5

7.5

6 / 30

Category: Clinical Laboratory

HE Agar is recommended by which pharmacopeia for Salmonella testing?

British Pharmacopoeia

Indian Pharmacopoeia

European Pharmacopoeia

United States Pharmacopoeia

7 / 30

Category: Clinical Laboratory

Lactose-fermenting bacteria like E. coli produce colonies that are:

Blue-green

Red

Colorless

Orange to salmon pink

8 / 30

Category: Clinical Laboratory

What differentiates HE Agar from MacConkey Agar?

Both B and C

Use of bile salts

Dual carbohydrate indicators

Inclusion of H₂S detection

9 / 30

Category: Clinical Laboratory

MacConkey Agar uses which inhibitor?

Bile salts

Sodium chloride

Brilliant green dye

Acid fuchsin

10 / 30

Category: Clinical Laboratory

Which component in HE Agar precipitates due to acid production?

Bile salts

A) Ferric ammonium citrate

Sodium thiosulfate

Bromothymol blue

11 / 30

Category: Clinical Laboratory

Shigella colonies on HE Agar are usually:

Yellow

Orange with bile precipitation

Black-centered

Green and transparent

12 / 30

Category: Clinical Laboratory

A key limitation of HE Agar is:

It kills all gram-negative bacteria

It cannot detect H₂S

A) It cannot differentiate Salmonella and Shigella

It may miss some Shigella strains requiring longer incubation

13 / 30

Category: Clinical Laboratory

What does a black precipitate in colonies indicate?

Gram-positive contamination

Lactose fermentation

H₂S production

Bile salt inhibition

14 / 30

Category: Clinical Laboratory

Why should HE Agar not be autoclaved?

Autoclaving promotes contamination

It becomes too acidic

It solidifies too quickly

Autoclaving degrades bile salts and indicators

15 / 30

Category: Clinical Laboratory

HE Agar should be incubated:

In CO₂

Anaerobically

At room temperature

Aerobically at 35–37°C

16 / 30

Category: Clinical Laboratory

Salmonella colonies on HE Agar typically appear:

Blue-green with black centers

Orange with black centers

Metallic green

Bright pink

17 / 30

Category: Clinical Laboratory

Which carbohydrate is not present in HE Agar?

Sucrose

Lactose

Salicin

Glucose

18 / 30

Category: Clinical Laboratory

Which medium was the first selective agar for enteric pathogens?

MacConkey Agar

HE Agar

EMB Agar

Endo Agar

19 / 30

Category: Clinical Laboratory

What is the primary purpose of HE Agar?

To identify viral pathogens

To grow gram-positive bacteria

To culture anaerobic bacteria

To isolate and differentiate Salmonella and Shigella

20 / 30

Category: Clinical Laboratory

Bromothymol blue in HE Agar acts as a:

Inhibitor

Carbohydrate source

Growth enhancer

pH indicator

21 / 30

Category: Clinical Laboratory

Why was HE Agar developed?

To improve recovery of Shigella

To replace all previous media

To detect viral pathogens

To inhibit Salmonella

22 / 30

Category: Clinical Laboratory

Bile salts in HE Agar primarily:

Promote gram-positive growth

Enhance lactose fermentation

Inhibit non-pathogenic gram-negative bacteria

Detect H₂S

23 / 30

Category: Clinical Laboratory

Which medium preceded HE Agar but overly inhibited Shigella?

EMB Agar

Salmonella-Shigella Agar

MacConkey Agar

XLD Agar

24 / 30

Category: Clinical Laboratory

Which organism is used for HE Agar quality control?

Pseudomonas aeruginosa

Candida albicans

Staphylococcus aureus

Salmonella Typhimurium

25 / 30

Category: Clinical Laboratory

Over-incubation of HE Agar may lead to:

False-negative lactose fermentation

Enhanced H₂S production

Bile salt precipitation

False-positive lactose fermentation

26 / 30

Category: Clinical Laboratory

Why must biochemical tests follow HE Agar screening?

To enhance colony color

To inhibit non-pathogens

To reduce incubation time

To confirm pathogen identity

27 / 30

Category: Clinical Laboratory

HE Agar is considered:

Both selective and differential

Only differential

Only selective

A non-selective medium

28 / 30

Category: Clinical Laboratory

What problem did EMB Agar solve compared to Endo Agar?

Growth of anaerobes

Inhibition of gram-positive bacteria

Detection of H₂S

Colony-based color change for lactose fermentation

29 / 30

Category: Clinical Laboratory

Which specimen is not suitable for HE Agar?

Food samples

Rectal swabs

Feces

Blood cultures

30 / 30

Category: Clinical Laboratory

Which organism may resemble Salmonella on HE Agar due to H₂S production?

Proteus

Streptococcus

Staphylococcus

E. coli

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Final Thoughts

The Hektoen Enteric Agar Mock Test is a valuable resource for reinforcing key concepts in enteric microbiology and diagnostic laboratory science. Regular practice improves identification skills, enhances exam performance, and builds confidence in interpreting stool culture results.

Continue practicing with other microbiology culture media mock tests to strengthen your foundation in clinical microbiology and infectious disease diagnosis.

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