Bacteriology: Escherichia coli pathotypes: 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: Escherichia coli pathotypes

Sample item

Several infants in a nursery develop prolonged watery diarrhoea without blood. Stool microscopy shows no leucocytes. Electron microscopy of the intestinal biopsy shows bacteria attached to the enterocytes with effacement of microvilli. Which mechanism is most likely responsible?

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

The answer and the reasoning

A. Attaching and effacing lesion produced through intimin-mediated adherence

Enteropathogenic E. coli causes infantile diarrhoea. It adheres through bundle-forming pili, then intimin binds a translocated receptor to produce attaching and effacing lesions that destroy the brush border. Invasion and Shiga toxin belong to other pathotypes.

Option by option

  • A. Attaching and effacing lesion produced through intimin-mediated adherence (correct)

    Correct. Microvillous effacement by adherent bacteria is the hallmark of enteropathogenic E. coli.

  • B. Heat-labile enterotoxin raising cyclic AMP

    Heat-labile toxin acts in enterotoxigenic E. coli and does not cause effacement.

  • C. Shiga toxin inhibiting the 60S ribosomal subunit

    Shiga toxin is produced by enterohaemorrhagic E. coli and produces bloody diarrhoea.

  • D. Invasion of colonic epithelium with intracellular spread

    Epithelial invasion belongs to enteroinvasive E. coli and produces dysentery with pus cells.

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 A, Attaching and effacing lesion produced through intimin-mediated adherence. Enteropathogenic E.

Why is "Heat-labile enterotoxin raising cyclic AMP" not the answer?

Heat-labile toxin acts in enterotoxigenic E. coli and does not cause effacement.

Why is "Shiga toxin inhibiting the 60S ribosomal subunit" not the answer?

Shiga toxin is produced by enterohaemorrhagic E. coli and produces bloody diarrhoea.

Why is "Invasion of colonic epithelium with intracellular spread" not the answer?

Epithelial invasion belongs to enteroinvasive E. coli and produces dysentery with pus cells.

What concept does this question test?

It tests Bacteriology: Escherichia coli pathotypes in Microbiology. coli causes infantile diarrhoea. It adheres through bundle-forming pili, then intimin binds a translocated receptor to produce attaching and effacing lesions that destroy the brush border. Invasion and Shiga toxin belong to other pathotypes.

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: Escherichia coli pathotypes?

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.