Microbiology · Gram-positive rods
Clostridioides difficile !
- Bacterium
- Gram-positive
- Contact
- Exam priority: high
A bacterium that causes diarrhoea and colitis, mostly after antibiotics; its spores resist alcohol and are removed by washing with soap and water.
Updated 2026-11-01
Also called: C. diff, Clostridium difficile (former name)
At a glance
- Gram
- Gram-positive
- Shape
- Rod with a subterminal spore
- Oxygen
- Obligate anaerobe
- Family
- Peptostreptococcaceae
- Stain
- Gram positive; spore former
Morphology
- Large Gram-positive rod
- Spores that survive months or years on surfaces
- Toxigenic (toxins A and B) and non-toxigenic strains
Transmission
- Faecal-oral: spores on surfaces, hands and objects
- Contact with infected patients in hospitals and nursing homes
- Antibiotics disturb the microbiota and let the bacterium take over
Isolation precautions
What the care team adds to standard precautions.
- Contact
- Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
Virulence factors
- Toxin A (enterotoxin) and toxin B (cytotoxin): inactivate Rho GTPases in colon cells
- Epithelial damage, inflammation and pseudomembranes
- Spores: environmental persistence and relapses
- Hypervirulent strains with higher toxin output
Diseases it causes
- C. difficile colitis, from diarrhoea to pseudomembranous colitis and toxic megacolon Clostridioides difficile infection →
Clinical picture
- Watery diarrhoea during or weeks after an antibiotic
- Fever, abdominal pain and leucocytosis
- Severe forms: ileus, toxic megacolon, sepsis
Diagnosis
- Only unformed stool from symptomatic patients is tested
- Stool detection of the toxins or their genes (PCR)
- Colonoscopy: yellowish pseudomembranes
- No test of cure: many patients stay colonised
Treatment
Stop the inciting antibiotic when possible. Oral vancomycin or fidaxomicin are preferred; metronidazole is now an alternative. Faecal microbiota transplant is used for multiple recurrences. Fulminant cases may need surgery.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Antibiotic stewardship
- Hand hygiene with soap and water: alcohol gel does not kill spores
- Contact precautions: gown and gloves, single room
- Cleaning with sporicidal disinfectants (for example, chlorine-based)
- Dedicated patient equipment
Test yourself
Think of the answer, then tap the question to see it.
Why is alcohol gel not enough for hand hygiene against C. difficile?
Because it does not kill the spores; soap-and-water washing removes them mechanically.
Which isolation precautions does a patient with C. difficile diarrhoea need?
Standard plus contact precautions: gown, gloves, single room and dedicated equipment.
Which drugs are preferred against C. difficile?
Oral vancomycin or fidaxomicin.
Which endoscopic finding is classic for severe C. difficile colitis?
Pseudomembranes: yellowish plaques stuck to the colonic mucosa.
Related
Related conditions
← Back to the group: Gram-positive rods
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: About C. diff (CDC, 2024); C. diff: Facts for Clinicians (CDC, 2024).
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Representative model, for educational purposes only.