🧭 When to suspect

Suspect Clostridioides difficile (C. diff) infection in any patient with new, unexplained diarrhoea, particularly when there has been recent antibiotic exposure:

• Characteristically watery, frequent and offensive

• Often with crampy lower abdominal pain

The decisive clinical reflex is simple: new diarrhoea + recent antibiotics = think C. diff.

Raise suspicion especially after the "4 Cs":

• Clindamycin

• Co-amoxiclav

• Cephalosporins

• Ciprofloxacin (and other fluoroquinolones)

Broad-spectrum penicillins and carbapenems also contribute. Other key risks:

• Age 65 and over

• Recent hospital or care-home stay

• Proton pump inhibitor (PPI) use

• Frailty

• Immunosuppression

The pathology is toxin-mediated, not overgrowth alone. Antibiotics disrupt the protective gut flora, allowing toxigenic C. difficile to flourish.

It is the toxins (A and B) that injure the colonic mucosa and produce disease ranging from mild diarrhoea to:

• Pseudomembranous colitis

• Toxic megacolon

• Perforation and death

This matters for diagnosis: detecting the organism is not the same as detecting active toxin.

Clostridioides difficile infection (CDI) is no longer a hospital-only problem – community-onset cases have been rising in England, so the diagnosis belongs firmly in the primary-care differential.

To manage it:

• Stratify by severity

• Recognise life-threatening disease early

Severity	Defining features
Mild	• Normal white cell count (WCC) • Typically fewer than 3 loose stools per day
Moderate	• Raised WCC but below 15 × 10⁹/L • Typically 3–5 loose stools per day
Severe	WCC above 15 × 10⁹/L, or creatinine risen > 50% above baseline, or temperature > 38.5°C, or evidence of severe colitis. Stool frequency is a less reliable marker here.
Life-threatening	Hypotension, partial or complete ileus, toxic megacolon, or CT evidence of severe disease.

Source: NICE NG199 · UKHSA

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