Bacteriology: Ehrlichia chaffeensis: 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: Ehrlichia chaffeensis

Sample item

A hunter from the central United States has fever, leukopenia, thrombocytopenia and raised transaminases a week after a tick bite. A peripheral smear shows mulberry-like cytoplasmic inclusions in monocytes. Which organism and treatment fit best?

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

The answer and the reasoning

C. Ehrlichia chaffeensis, treated with doxycycline

Ehrlichia chaffeensis infects monocytes and forms intracytoplasmic clusters called morulae. It causes human monocytic ehrlichiosis with leukopenia and thrombocytopenia, and doxycycline is the treatment of choice.

Option by option

  • A. Borrelia burgdorferi, treated with ceftriaxone

    Borrelia is a spirochaete and does not form intracellular inclusions in leukocytes.

  • B. Babesia microti, treated with atovaquone and azithromycin

    Babesia lives inside red cells and shows ring forms and Maltese crosses, not monocyte morulae.

  • C. Ehrlichia chaffeensis, treated with doxycycline (correct)

    Correct. Morulae in monocytes indicate Ehrlichia, and doxycycline is the drug of choice.

  • D. Francisella tularensis, treated with streptomycin

    Francisella causes ulceroglandular or pneumonic disease and is not seen as inclusions in monocytes.

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.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Ehrlichia chaffeensis, treated with doxycycline. Ehrlichia chaffeensis infects monocytes and forms intracytoplasmic clusters called morulae.

Why is "Borrelia burgdorferi, treated with ceftriaxone" not the answer?

Borrelia is a spirochaete and does not form intracellular inclusions in leukocytes.

Why is "Babesia microti, treated with atovaquone and azithromycin" not the answer?

Babesia lives inside red cells and shows ring forms and Maltese crosses, not monocyte morulae.

Why is "Francisella tularensis, treated with streptomycin" not the answer?

Francisella causes ulceroglandular or pneumonic disease and is not seen as inclusions in monocytes.

What concept does this question test?

It tests Bacteriology: Ehrlichia chaffeensis in Microbiology. It causes human monocytic ehrlichiosis with leukopenia and thrombocytopenia, and doxycycline is the treatment of choice.

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: Ehrlichia chaffeensis?

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.