Mycology: Epidermophyton floccosum: 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 · Mycology: Epidermophyton floccosum

Sample item

A man has an erythematous scaly groin plaque with a raised active edge that spares the scrotum. Culture grows a fungus with smooth club-shaped macroconidia in clusters and no microconidia. Which genus is this, and which sites does it infect?

AMicrosporum, which infects skin and hair but not nailsBTrichophyton, which has abundant microconidia and infects skin, hair and nailsCMalassezia, which causes pityriasis versicolorDEpidermophyton, which infects skin and nails but never hair

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

The answer and the reasoning

D. Epidermophyton, which infects skin and nails but never hair

Epidermophyton floccosum is a dermatophyte producing smooth, thin-walled, club-shaped macroconidia and no microconidia, and is a common cause of tinea cruris. It invades skin and nails but not hair. Microsporum infects skin and hair, and Trichophyton may involve all three.

Option by option

A. Microsporum, which infects skin and hair but not nails
Microsporum has rough spindle-shaped macroconidia and does not usually infect nails.
B. Trichophyton, which has abundant microconidia and infects skin, hair and nails
Trichophyton shows numerous microconidia, which are absent here.
C. Malassezia, which causes pityriasis versicolor
Malassezia is a lipophilic yeast and not a dermatophyte producing macroconidia.
D. Epidermophyton, which infects skin and nails but never hair (correct)
Correct. Club-shaped macroconidia without microconidia identify Epidermophyton, which spares hair.

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 D, Epidermophyton, which infects skin and nails but never hair. Epidermophyton floccosum is a dermatophyte producing smooth, thin-walled, club-shaped macroconidia and no microconidia, and is a common cause of tinea cruris.

Why is "Microsporum, which infects skin and hair but not nails" not the answer?

Microsporum has rough spindle-shaped macroconidia and does not usually infect nails.

Why is "Trichophyton, which has abundant microconidia and infects skin, hair…" not the answer?

Trichophyton shows numerous microconidia, which are absent here.

Why is "Malassezia, which causes pityriasis versicolor" not the answer?

Malassezia is a lipophilic yeast and not a dermatophyte producing macroconidia.

What concept does this question test?

It tests Mycology: Epidermophyton floccosum in Microbiology. It invades skin and nails but not hair. Microsporum infects skin and hair, and Trichophyton may involve all three.

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 Mycology: Epidermophyton floccosum?

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.