General microbiology: normal flora: 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 · General microbiology: normal flora

Sample item

A woman develops itching and a thick, white, curd-like vaginal discharge after a 10-day course of a broad-spectrum antibiotic. Which mechanism most directly explains this?

AAntibiotic-induced immunodeficiencyBDirect stimulation of Candida hyphae by the drugCLoss of vaginal lactobacilli that maintain acidity and suppress yeastsDAcquisition of Candida from her partner

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

The answer and the reasoning

C. Loss of vaginal lactobacilli that maintain acidity and suppress yeasts

Lactobacilli of the vaginal flora ferment glycogen to lactic acid, keeping the pH low, and compete with other organisms. Broad-spectrum antibiotics reduce them, and Candida albicans, which is often a commensal, overgrows. This is an example of a disturbance of normal flora.

Option by option

A. Antibiotic-induced immunodeficiency
Antibiotics do not cause immunodeficiency.
B. Direct stimulation of Candida hyphae by the drug
Antibiotics do not stimulate hyphal growth.
C. Loss of vaginal lactobacilli that maintain acidity and suppress yeasts (correct)
Correct. Loss of protective lactobacilli permits overgrowth of Candida.
D. Acquisition of Candida from her partner
Candida is usually already present as a commensal, and acquisition is not required.

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 C, Loss of vaginal lactobacilli that maintain acidity and suppress yeasts. Lactobacilli of the vaginal flora ferment glycogen to lactic acid, keeping the pH low, and compete with other organisms.

Why is "Antibiotic-induced immunodeficiency" not the answer?

Antibiotics do not cause immunodeficiency.

Why is "Direct stimulation of Candida hyphae by the drug" not the answer?

Antibiotics do not stimulate hyphal growth.

Why is "Acquisition of Candida from her partner" not the answer?

Candida is usually already present as a commensal, and acquisition is not required.

What concept does this question test?

It tests General microbiology: normal flora in Microbiology. Broad-spectrum antibiotics reduce them, and Candida albicans, which is often a commensal, overgrows. This is an example of a disturbance of normal flora.

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 General microbiology: normal flora?

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.