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

A 20-year-old man has fever, tenesmus and stools containing blood, mucus and many pus cells. Culture yields a non-motile, late lactose-fermenting Gram-negative bacillus that gives a positive Sereny test, and Shigella is excluded biochemically. Which E. coli pathotype is responsible?

AEnteroinvasive E. coliBEnteropathogenic E. coliCEnterotoxigenic E. coliDEnterohaemorrhagic E. coli

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

The answer and the reasoning

A. Enteroinvasive E. coli

Enteroinvasive E. coli carries an invasion plasmid, penetrates and multiplies in colonic epithelial cells and spreads cell to cell, causing a Shigella-like dysentery. It is non-motile and a late lactose fermenter, and the Sereny test (keratoconjunctivitis in guinea pig) is positive. The other pathotypes do not invade.

Option by option

A. Enteroinvasive E. coli (correct)
Correct. Invasion, pus cells and a Shigella-like picture indicate enteroinvasive E. coli.
B. Enteropathogenic E. coli
Enteropathogenic E. coli causes watery infant diarrhoea by adherence and effacement.
C. Enterotoxigenic E. coli
Enterotoxigenic E. coli causes watery travellers' diarrhoea through toxins without invasion.
D. Enterohaemorrhagic E. coli
Enterohaemorrhagic E. coli causes bloody diarrhoea with little fever and few pus cells, and does not invade.

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 A, Enteroinvasive E. coli. Enteroinvasive E.

Why is "Enteropathogenic E. coli" not the answer?

Enteropathogenic E. coli causes watery infant diarrhoea by adherence and effacement.

Why is "Enterotoxigenic E. coli" not the answer?

Enterotoxigenic E. coli causes watery travellers' diarrhoea through toxins without invasion.

Why is "Enterohaemorrhagic E. coli" not the answer?

Enterohaemorrhagic E. coli causes bloody diarrhoea with little fever and few pus cells, and does not invade.

What concept does this question test?

It tests Bacteriology: Escherichia coli pathotypes in Microbiology. coli carries an invasion plasmid, penetrates and multiplies in colonic epithelial cells and spreads cell to cell, causing a Shigella-like dysentery. It is non-motile and a late lactose fermenter, and the Sereny test (keratoconjunctivitis in guinea pig) is positive. The other pathotypes do not invade.

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: 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.