Definition
Clostridium difficile (C. difficile) infection is a bacterial infection that causes diarrhea and inflammation of the colon (colitis). It is primarily associated with antibiotic use and is a common cause of hospital-acquired infections.

Pathogenesis
C. difficile produces toxins that damage the intestinal wall, leading to inflammation. Antibiotic use disrupts the normal gut flora, allowing the bacterium to overgrow. Risk factors include prior antibiotic therapy, hospitalization, immunosuppression, and advanced age.

Diagnosis
Diagnosis is made by detecting C. difficile toxins in stool samples or through molecular methods (PCR). Endoscopy or CT scans may be used in severe cases to confirm pseudomembranous colitis and toxic megacolon.

Treatment

  • Mild to moderate infection: Discontinuation of the responsible antibiotic and administration of specific antibiotic therapy (e.g., oral metronidazole or vancomycin).
  • Severe infection: Oral vancomycin or fidaxomicin, along with supportive care (hydration, nutrition).
  • Recurrent infections: Use of probiotics or fecal microbiota transplantation (FMT) to restore normal gut flora.

Early diagnosis and treatment are crucial to prevent complications such as toxic megacolon and bowel perforation. Preventive measures, including judicious use of antibiotics and strict hygiene protocols, are essential for reducing the spread of infection.

Other infectious causes such as salmonellosis and norovirus must be excluded, as must a flare of inflammatory bowel disease.

Frequently asked questions

Why does it occur after antibiotics?

Antibiotics disturb the normal gut flora that would otherwise keep the organism in check. Once that balance is lost, Clostridioides difficile multiplies and produces toxins that damage the colonic mucosa. This is why the infection typically appears during or in the weeks following a course of antibiotics.

Is it contagious?

Yes. The spores are transmitted by the faecal oral route and survive on surfaces for long periods. Alcohol hand gel does not destroy them, so washing with soap and water is required, and surfaces need chlorine based disinfection. Patients in hospital are isolated for this reason.

What if it recurs?

Recurrence occurs in a substantial minority of patients and does not mean treatment failed. Management differs from the first episode and may involve a different antibiotic regimen, a tapering course, or faecal microbiota transplantation in recurrent disease, which has high success rates.

Sources

  • van Prehn J et al., European Society of Clinical Microbiology and Infectious Diseases: 2021 update on the treatment guidance document for Clostridioides difficile infection. https://doi.org/10.1016/j.cmi.2021.09.038

Content last updated: September 2026 (14/09/2026).