Bacterial motility: Listeria monocytogenes: 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 · Bacterial motility: Listeria monocytogenes

Sample item

Cerebrospinal fluid from a neonate with meningitis grows Gram-positive coccobacilli. A hanging-drop preparation from a broth culture incubated at room temperature is examined. What is the expected motility?

ADarting motility in all temperaturesBSwarming growth that spreads across the whole plateCTumbling motility, which is reduced at 37 degrees CDNo motility at any temperature

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

The answer and the reasoning

C. Tumbling motility, which is reduced at 37 degrees C

Listeria monocytogenes expresses peritrichous flagella mainly at 20 to 25 degrees C, so it shows a characteristic end-over-end tumbling motility and an umbrella pattern in semisolid agar at that temperature. At 37 degrees C flagellar expression is much reduced. Darting motility is typical of Vibrio and Campylobacter.

Option by option

A. Darting motility in all temperatures
Darting motility describes comma-shaped organisms such as Vibrio cholerae and Campylobacter.
B. Swarming growth that spreads across the whole plate
Swarming is typical of Proteus on agar, not Listeria.
C. Tumbling motility, which is reduced at 37 degrees C (correct)
Correct. Tumbling motility at 25 degrees C is a characteristic of Listeria.
D. No motility at any temperature
Listeria is motile at room temperature, so it is not non-motile.

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, Tumbling motility, which is reduced at 37 degrees C. Listeria monocytogenes expresses peritrichous flagella mainly at 20 to 25 degrees C, so it shows a characteristic end-over-end tumbling motility and an umbrella pattern in semisolid agar at that temperature.

Why is "Darting motility in all temperatures" not the answer?

Darting motility describes comma-shaped organisms such as Vibrio cholerae and Campylobacter.

Why is "Swarming growth that spreads across the whole plate" not the answer?

Swarming is typical of Proteus on agar, not Listeria.

Why is "No motility at any temperature" not the answer?

Listeria is motile at room temperature, so it is not non-motile.

What concept does this question test?

It tests Bacterial motility: Listeria monocytogenes in Microbiology. At 37 degrees C flagellar expression is much reduced. Darting motility is typical of Vibrio and Campylobacter.

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 Bacterial motility: Listeria monocytogenes?

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.