🧭 When to suspect

Suspect Clostridioides difficile infection (CDI) in any patient who develops new diarrhoea (Bristol Stool type 5–7) during, or in the weeks following (up to around 8 weeks after), a course of antibiotics.

C. difficile – reclassified from Clostridium to Clostridioides in 2016 – is a spore-forming, toxin-producing anaerobe that overgrows when antibiotics disrupt the normal gut flora. In its severe form it causes pseudomembranous colitis.

The antibiotics most strongly associated are the “4 Cs”, though any antibiotic can trigger it:

• Clindamycin

• Cephalosporins

• Co-amoxiclav

• Ciprofloxacin (fluoroquinolones)

Risk is higher with:

• Increasing age (> 65)

• Recent hospitalisation or care-home residence

• Proton pump inhibitor (PPI) use

• Immunosuppression

• Previous CDI

For every case, three assessments drive management:

• Whether it is a first or further episode (relapse < 12 weeks, recurrence > 12 weeks after symptom resolution)

• The severity

• Individual risk factors for complications or recurrence

Severity (PHE)	Defining features	Action
Mild	• Normal white cell count (WCC) • Typically < 3 loose stools/day	• Treat in community • Oral vancomycin • Safety-net
Moderate	• Raised WCC < 15 × 10⁹/L • Typically 3–5 loose stools/day	• Treat in community • Oral vancomycin • Closer review
Severe	WCC > 15 × 10⁹/L, or creatinine > 50% above baseline, or temp > 38.5°C, or severe colitis	Urgent specialist advice ± admission
Life-threatening	Hypotension, partial/complete ileus, toxic megacolon, or CT evidence of severe disease	• 999 or emergency admission • Surgical + specialist input

Note that for a first episode, severity changes the urgency and monitoring, not the first-line drug – mild, moderate and severe disease all receive oral vancomycin.

Source: NICE NG199 · UKHSA

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Diarrhoea – Abx associated - Clostridium Difficile Infection (CDI)

🧭 When to suspect