Bacteriology: Actinomyces: 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: Actinomyces

Sample item

A 32-year-old woman with an intrauterine device in place for 7 years has chronic pelvic pain and a tubo-ovarian mass. Pus shows yellow sulphur granules containing Gram-positive branching filaments that are not acid-fast. Which is the first-line drug?

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

The answer and the reasoning

B. High-dose penicillin G followed by oral penicillin or amoxicillin for months

Actinomyces israelii is an anaerobic, non-acid-fast commensal of the mouth and gut that causes cervicofacial, thoracic, abdominal and pelvic actinomycosis, including pelvic infection linked to long-standing IUCDs. Prolonged high-dose penicillin is first line, together with drainage and device removal.

Option by option

  • A. Metronidazole alone

    Actinomyces is intrinsically resistant to metronidazole, so it fails even though the organism is anaerobic.

  • B. High-dose penicillin G followed by oral penicillin or amoxicillin for months (correct)

    Correct. Penicillin remains the drug of choice, given for months because of the dense fibrotic lesion.

  • C. Fluconazole

    Fluconazole treats fungal infections, and these filaments are bacterial.

  • D. Trimethoprim-sulfamethoxazole

    Cotrimoxazole is the drug of choice for Nocardia, which is aerobic and partially acid-fast.

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 B, High-dose penicillin G followed by oral penicillin or amoxicillin for months. Actinomyces israelii is an anaerobic, non-acid-fast commensal of the mouth and gut that causes cervicofacial, thoracic, abdominal and pelvic actinomycosis, including pelvic infection linked to long-standing IUCDs.

Why is "Metronidazole alone" not the answer?

Actinomyces is intrinsically resistant to metronidazole, so it fails even though the organism is anaerobic.

Why is "Fluconazole" not the answer?

Fluconazole treats fungal infections, and these filaments are bacterial.

Why is "Trimethoprim-sulfamethoxazole" not the answer?

Cotrimoxazole is the drug of choice for Nocardia, which is aerobic and partially acid-fast.

What concept does this question test?

It tests Bacteriology: Actinomyces in Microbiology. Prolonged high-dose penicillin is first line, together with drainage and device removal.

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: Actinomyces?

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.