Bacteriology: Mycobacterium leprae cultivation: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Bacteriology: Mycobacterium leprae cultivation

Sample item

Mycobacterium leprae does not grow on artificial media but multiplies in the footpads of mice and in the nine-banded armadillo. Which property of these hosts explains this?

AA high carbon dioxide tension in the tissuesBA lack of acid-fast stainable lipidsCCooler tissue temperature suited to the organismDAbsence of any macrophages in the footpad

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Cooler tissue temperature suited to the organism

M. leprae grows best at about 30 to 33 degrees Celsius, which explains its predilection for skin, peripheral nerves and the cooler parts of the body. The mouse footpad and the armadillo, whose body temperature is low, support its multiplication. This is used for propagation, drug testing and studying viability.

Option by option

A. A high carbon dioxide tension in the tissues
Carbon dioxide tension is not what allows growth of this organism.
B. A lack of acid-fast stainable lipids
Acid-fastness is a property of the bacillus and does not depend on host lipids.
C. Cooler tissue temperature suited to the organism (correct)
Correct. The low temperature of the footpad and the armadillo allows growth.
D. Absence of any macrophages in the footpad
Macrophages are the host cells for M. leprae and are present in the footpad.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Cooler tissue temperature suited to the organism. M.

Why is "A high carbon dioxide tension in the tissues" not the answer?

Carbon dioxide tension is not what allows growth of this organism.

Why is "A lack of acid-fast stainable lipids" not the answer?

Acid-fastness is a property of the bacillus and does not depend on host lipids.

Why is "Absence of any macrophages in the footpad" not the answer?

Macrophages are the host cells for M. leprae and are present in the footpad.

What concept does this question test?

It tests Bacteriology: Mycobacterium leprae cultivation in Microbiology. leprae grows best at about 30 to 33 degrees Celsius, which explains its predilection for skin, peripheral nerves and the cooler parts of the body. The mouse footpad and the armadillo, whose body temperature is low, support its multiplication. This is used for propagation, drug testing and studying viability.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Bacteriology: Mycobacterium leprae cultivation?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.