Chlamydiae: 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 · Chlamydiae

Sample item

Which statement about the life cycle of Chlamydia trachomatis is correct?

AThe elementary body is the infectious form and the reticulate body is the replicating formBThe reticulate body is infectious and the elementary body replicatesCIt is a free-living organism with peptidoglycan-rich cell wallDIt grows extracellularly on blood agar

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

The answer and the reasoning

A. The elementary body is the infectious form and the reticulate body is the replicating form

Chlamydiae are obligate intracellular bacteria. The small, metabolically inert elementary body enters the cell by endocytosis and transforms into a reticulate body, which divides within an inclusion and then reorganises into new elementary bodies. They need cell culture or nucleic acid tests for detection.

Option by option

A. The elementary body is the infectious form and the reticulate body is the replicating form (correct)
Correct. Elementary bodies infect and reticulate bodies replicate.
B. The reticulate body is infectious and the elementary body replicates
The roles of the two forms are reversed in this option.
C. It is a free-living organism with peptidoglycan-rich cell wall
They are not free-living and lack a conventional peptidoglycan layer.
D. It grows extracellularly on blood agar
Chlamydiae cannot grow on cell-free media because they are obligate intracellular parasites.

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 A, The elementary body is the infectious form and the reticulate body is the replicating form. Chlamydiae are obligate intracellular bacteria.

Why is "The reticulate body is infectious and the elementary body replicates" not the answer?

The roles of the two forms are reversed in this option.

Why is "It is a free-living organism with peptidoglycan-rich cell wall" not the answer?

They are not free-living and lack a conventional peptidoglycan layer.

Why is "It grows extracellularly on blood agar" not the answer?

Chlamydiae cannot grow on cell-free media because they are obligate intracellular parasites.

What concept does this question test?

It tests Chlamydiae in Microbiology. The small, metabolically inert elementary body enters the cell by endocytosis and transforms into a reticulate body, which divides within an inclusion and then reorganises into new elementary bodies. They need cell culture or nucleic acid tests for detection.

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 Chlamydiae?

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.