Bacteriology: rapid-growing mycobacteria: 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: rapid-growing mycobacteria

Sample item

Six weeks after a cosmetic abdominal liposuction at a small clinic, a 34-year-old woman has multiple discharging subcutaneous abscesses that do not respond to cephalexin. Pus shows acid-fast bacilli, and Lowenstein-Jensen culture shows growth within 5 days. She has no pulmonary disease. Which is the most likely organism and treatment approach?

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

The answer and the reasoning

D. M. abscessus or M. chelonae, treated with a macrolide-based multidrug regimen

Rapid growers such as Mycobacterium abscessus, chelonae and fortuitum form visible colonies within 7 days and cause post-procedural skin and soft tissue infection, often from contaminated water or instruments. They are resistant to standard antituberculous drugs, so treatment uses agents such as clarithromycin or azithromycin with amikacin and cefoxitin, guided by susceptibility testing, with surgical debridement.

Option by option

  • A. M. marinum, which is treated with isoniazid alone

    M. marinum is slow-growing and is not treated with isoniazid alone.

  • B. M. tuberculosis, treated with standard four-drug antituberculous therapy

    M. tuberculosis takes 2 to 6 weeks to grow and would not usually cause post-liposuction abscesses.

  • C. M. leprae, which grows on LJ medium within a week

    M. leprae has never been grown on artificial media.

  • D. M. abscessus or M. chelonae, treated with a macrolide-based multidrug regimen (correct)

    Growth within 5 days indicates a rapid grower that needs a macrolide-based regimen, not antituberculous drugs.

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 D, M. abscessus or M. chelonae, treated with a macrolide-based multidrug regimen. Rapid growers such as Mycobacterium abscessus, chelonae and fortuitum form visible colonies within 7 days and cause post-procedural skin and soft tissue infection, often from contaminated water or instruments.

Why is "M. marinum, which is treated with isoniazid alone" not the answer?

M. marinum is slow-growing and is not treated with isoniazid alone.

Why is "M. tuberculosis, treated with standard four-drug antituberculous ther…" not the answer?

M. tuberculosis takes 2 to 6 weeks to grow and would not usually cause post-liposuction abscesses.

Why is "M. leprae, which grows on LJ medium within a week" not the answer?

M. leprae has never been grown on artificial media.

What concept does this question test?

It tests Bacteriology: rapid-growing mycobacteria in Microbiology. They are resistant to standard antituberculous drugs, so treatment uses agents such as clarithromycin or azithromycin with amikacin and cefoxitin, guided by susceptibility testing, with surgical debridement.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: rapid-growing mycobacteria?

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.