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Answer 15 of 50

Gastrointestinal Infection

A 3-year-old who is still in nappies is admitted with 3 days of bloody diarrhoea and crampy abdominal pain. He is alert and mildly dehydrated, and stool studies have been sent while oral rehydration continues on an open ward.

Which of these organisms, if isolated, would require admission with strict contact isolation in a single room?

Correct answer: D — Clostridioides difficile

Only Clostridioides difficile forms spores that survive alcohol hand rub and routine cleaning, so it is the one that demands a single room with contact precautions.

Spores are shed in huge numbers in diarrhoeal stool and persist on surfaces for months, so the environment rather than the patient is the reservoir that infects the next child.
Alcohol hand rub does not kill spores; hands must be washed with soap and water and the room decontaminated with a sporicidal agent such as hypochlorite.
A child still in nappies cannot contain stool, which is exactly why incontinence escalates a general contact precaution into a single room requirement, continued until 48 hours after the diarrhoea stops.
The other listed pathogens are managed with hand hygiene and contact precautions while symptomatic; alcohol rub is effective against them and no sporicidal cleaning is needed.
Testing is not indicated under 12 months and is interpreted cautiously in toddlers because asymptomatic carriage is common, but once it is the working diagnosis the isolation rules apply.

★ Clinical pearl

Alcohol gel does not touch spores; a child with Clostridioides difficile needs a single room and soap and water at every exit.

Exam note

The Escherichia coli option is written without qualification, so it means the ordinary enteric strains, which need only standard precautions and hand hygiene; even a Shiga toxin producing strain would call for contact precautions and public health notification rather than a sporicidal single room. The isolation rule in this question turns on spores, which alcohol rub does not kill, and Clostridioides difficile is the only listed organism that forms them.

Go deeper — why the other options fail, and what candidates recalled

Option	Why not
A	Non-typhoidal Salmonella needs hand hygiene and contact precautions while a child is incontinent, but most cases are managed at home without antibiotics and no single room with sporicidal cleaning is required.
B	Cryptosporidium causes watery rather than bloody diarrhoea in the immunocompetent child; its chlorine resistance matters for swimming pools, not for ward isolation.
C	Escherichia coli as written covers the ordinary enteric strains, handled with standard precautions and hand hygiene; even the Shiga toxin producing strains need contact precautions and public health notification rather than a sporicidal single room regimen.

What candidates actually recalled: Clostridium difficile[?] (found in 3 recall sets)

Consistent with CDC isolation precautions / AAP Red Book 2024

Case Complete