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Health condition · Clinically reviewed

C. difficile, testing, fidaxomicin and when to consider FMT.

A toxin-driven colitis that follows antibiotics and hospital exposure. Modern UK care is fidaxomicin first, careful infection control, and faecal microbiota transplant for those who keep relapsing.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE NG199, UKHSA (PHE), IDSA/SHEA and ESCMID standards you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including fidaxomicin first-line, bezlotoxumab and faecal microbiota transplant.

Key facts

C. difficile at a glance.

The essentials, in plain English. What it is, who gets it, why antibiotics matter, and how it is treated in the UK today.

  • What it is

    Clostridioides difficile is a spore-forming anaerobic bacterium whose toxins A and B drive an inflammatory colitis, from mild diarrhoea to pseudomembranous colitis and toxic megacolon.

  • Where it comes from

    A leading cause of healthcare-associated diarrhoea in the UK, with community-acquired cases now increasing outside hospital settings.

  • Main trigger

    Antibiotic exposure that disrupts the gut microbiota. Cephalosporins, clindamycin, fluoroquinolones and carbapenems carry the highest risk, but any antibiotic can precipitate CDI.

  • Who is most at risk

    People over 65, hospital and care-home residents, PPI users, the immunocompromised, patients with IBD and anyone with a previous episode.

  • Recurrence

    20 to 30 per cent of patients relapse after a first episode, and the risk rises with each subsequent recurrence.

  • Foundation therapy

    Fidaxomicin or oral vancomycin, guided by NICE NG199. Faecal microbiota transplant is the standard for multiply recurrent disease.

Why this guide matters

Treatable, but a moving target.

The playbook has shifted. Fidaxomicin is now first-line, bezlotoxumab addresses recurrence, and faecal microbiota transplant is a proven cure for relapsing disease.

  • Antibiotics are the main trigger

    Any antibiotic can precipitate CDI, but cephalosporins, clindamycin, fluoroquinolones and carbapenems carry the highest risk.

  • Fidaxomicin is now first-line

    NICE NG199 recommends fidaxomicin for first episodes and recurrences to reduce the relapse rate compared with vancomycin.

  • FMT changes recurrent disease

    For patients with two or more relapses, faecal microbiota transplant delivers cure rates above 90 per cent and should be discussed early.

How the diagnosis is made

From suspicion to confirmed CDI.

The steps a UK hospital team will normally follow, in order. Recognition, isolation, laboratory confirmation and a notification to UKHSA within 24 hours.

  1. 01

    Assessing

    Recognising the clinical picture

    New or worsening loose stools (typically three or more in 24 hours) in a patient with recent antibiotics, hospital stay or care-home residence.

  2. 02

    Assessing

    Severity assessment

    White cell count, creatinine, lactate, blood pressure, temperature and abdominal signs classify disease as mild, severe or fulminant.

  3. 03

    Assessing

    Isolation and infection control

    Single room, contact precautions, soap and water hand hygiene (alcohol gel does not kill spores), PPE and terminal cleaning with a chlorine-based disinfectant.

  4. 04

    Confirming

    Two-step stool testing

    GDH antigen or NAAT toxin PCR as a sensitive screen, then a confirmatory toxin A/B EIA. Only diarrhoeal stool is tested; formed stools are not.

  5. 05

    Confirming

    Bloods and imaging

    FBC, U&Es, lactate and inflammatory markers. CXR, AXR or CT if perforation, ileus or toxic megacolon is suspected.

  6. 06

    Confirming

    Selective flexible sigmoidoscopy

    Reserved for diagnostic doubt or when direct visualisation of pseudomembranes will change management.

  7. 07

    Escalating

    UKHSA notification and MDT

    Notify UKHSA (formerly PHE) within 24 hours and involve infectious diseases, microbiology, gastroenterology, IPC and surgery where appropriate.

Typical timeline: from stool sample to a confirmed diagnosis in 24 to 48 hours.

Symptoms

What CDI actually looks like.

A spectrum from watery diarrhoea to sepsis and toxic megacolon. The features below help clinicians classify severity and decide who needs escalation.

  • Profuse watery diarrhoea

    Usually more than three loose stools in 24 hours, often with a characteristic foul odour.

  • Cramping abdominal pain

    Lower abdominal cramps and tenderness that ease briefly after a bowel motion.

  • Fever and leucocytosis

    Pyrexia and a rising white cell count signal an inflammatory response and a shift toward severe disease.

  • Pseudomembranous colitis

    Yellow-white plaques on the colonic mucosa at endoscopy, the classical finding in more advanced CDI.

  • Toxic megacolon and ileus

    Colonic dilatation, abdominal distension and absent bowel sounds mark fulminant disease and demand surgical input.

  • Sepsis and hypotension

    Rising lactate, tachycardia and low blood pressure indicate systemic involvement and the need for critical care.

  • Recurrent episodes

    One in four to one in three patients relapse, typically within eight weeks of finishing treatment.

  • Red flag: perforation

    Peritonism, free gas on imaging or refractory shock warrants urgent surgical review for colectomy or diverting ileostomy.

Treatment

How C. difficile is treated in the UK.

Stop the trigger, treat with fidaxomicin or vancomycin, add bezlotoxumab or FMT for recurrence, and escalate rapidly for fulminant disease. Ridinilazole is emerging as a narrower-spectrum alternative.

  • Stop the trigger

    Discontinue the precipitating antibiotic where clinically safe and review the ongoing need for PPIs or H2 blockers.

  • Fidaxomicin (first-line)

    NICE NG199 recommends fidaxomicin 200 mg twice daily for 10 days for first episodes and recurrences, based on lower relapse rates versus vancomycin.

  • Oral vancomycin

    Vancomycin 125 mg four times daily for 10 days remains an evidence-based alternative, particularly where fidaxomicin is unavailable.

  • Severe disease

    Oral vancomycin 125 mg four times daily with escalation to fidaxomicin or the addition of IV metronidazole where oral absorption is a concern.

  • Fulminant disease

    High-dose oral vancomycin 500 mg four times daily with rectal vancomycin enema and IV metronidazole, plus urgent surgical review.

  • Bezlotoxumab

    A monoclonal antibody against toxin B given alongside standard therapy to reduce recurrence in higher-risk patients.

  • Faecal microbiota transplant

    The standard of care for multiply recurrent CDI, with cure rates above 90 per cent. Delivered as colonoscopic, nasoenteric or oral capsule preparations.

  • Supportive and infection control

    IV fluids, electrolyte replacement, nutrition, isolation, PPE, chlorine-based cleaning and antimicrobial stewardship for every patient.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and international specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, hospital team or gastroenterologist knows your history and can tell you which parts of this guide apply to you. If in doubt, get seen.

  • NICE. Clostridioides difficile infection: antimicrobial prescribing (NG199).

  • UK Health Security Agency (UKHSA, formerly Public Health England). Guidance on the management and treatment of Clostridioides difficile infection.

  • IDSA/SHEA. Clinical practice guidelines for Clostridioides difficile infection in adults and children.

  • ESCMID. Treatment guidance document for Clostridioides difficile infection in adults.

Red flags

When CDI needs urgent escalation.

Most cases settle with fidaxomicin or vancomycin. These are the situations that do not, and where surgical or specialist input is needed without delay.

  • Fulminant colitis

    Hypotension, ileus or toxic megacolon needs urgent surgical review for subtotal colectomy or diverting loop ileostomy with antegrade lavage.

  • Suspected perforation

    Peritonism, guarding or free gas on imaging is a surgical emergency. Do not delay theatre for further tests.

  • Rising WCC and lactate

    A white cell count above 15 or lactate above 2.5 is a marker of severe disease and predicts deterioration.

  • Acute kidney injury

    Creatinine above 133 or a 1.5-fold rise from baseline defines severe CDI and prompts escalation of therapy.

  • Multiple recurrences

    Two or more recurrences should trigger a specialist referral for faecal microbiota transplant or extended pulsed regimens.

  • Immunocompromised host

    Patients on chemotherapy, high-dose steroids or biologics deteriorate faster and warrant earlier fidaxomicin and MDT input.

  • IBD flare mimic

    CDI in inflammatory bowel disease is easily missed and worsens outcomes. Test any IBD flare with fresh diarrhoea for C. difficile.

  • Care-home outbreak

    Two or more linked cases within a ward or care home is an outbreak signal and requires UKHSA notification and IPC involvement.

  • Do not use loperamide

    Antimotility agents can precipitate toxic megacolon in active CDI and should be avoided.

Living with it

Recovering, and preventing the next episode.

Four things that make the biggest difference during and after CDI. Hydration, meticulous hygiene, careful future antibiotic use, and knowing when to ask for FMT.

A quiet reminder

Repeat testing is not needed to prove cure.

Asymptomatic carriage of C. difficile is common after treatment. Symptoms, not stool tests, guide whether you are better.

  1. 01 Hydration

    Fluids and electrolytes first

    Oral rehydration is the priority. Seek urgent review if you cannot keep fluids down or your urine output drops.

  2. 02 Hygiene

    Soap and water beats alcohol gel

    C. difficile spores survive alcohol hand gel. Wash hands with soap and water and clean surfaces with a chlorine-based product.

  3. 03 Antibiotics

    Ask before starting another course

    Any future antibiotic can trigger a recurrence. Tell every clinician that you have had CDI so alternatives can be considered.

  4. 04 Escalate

    Do not accept a third relapse

    If CDI keeps coming back, ask for a gastroenterology referral for faecal microbiota transplant or bezlotoxumab.

Frequently asked

Everything we get asked about C. difficile.

Quick answers on testing, fidaxomicin, faecal microbiota transplant and hospital infection control.

  • What is C. difficile infection?

    It is an infection of the large bowel caused by Clostridioides difficile, a spore-forming anaerobic bacterium. Its toxins A and B damage the colonic lining and trigger inflammation, ranging from mild diarrhoea to pseudomembranous colitis, toxic megacolon and, in the most severe cases, sepsis and death.

  • How do you catch it?

    Most cases follow antibiotic use that disrupts the normal gut microbiota, allowing C. difficile spores to germinate and produce toxin. Spores spread easily in hospitals and care homes on hands, surfaces and equipment. Community-acquired cases outside these settings are increasing.

  • How is it diagnosed?

    UK laboratories use a two-step algorithm on a diarrhoeal stool sample: a sensitive screen with either the GDH antigen or a NAAT toxin PCR, followed by a confirmatory toxin A/B EIA. Formed stools are not tested and asymptomatic carriage is common, so testing is reserved for patients with genuine diarrhoea.

  • Is fidaxomicin better than vancomycin?

    NICE NG199 now recommends fidaxomicin first-line for both first episodes and recurrences because the OPT-80 trials showed lower recurrence rates than oral vancomycin. Oral vancomycin remains an effective alternative and is used in fulminant disease at higher doses, often combined with a rectal enema and IV metronidazole.

  • What is a faecal microbiota transplant?

    FMT transfers screened stool from a healthy donor into the patient’s bowel, most often by colonoscopy or oral capsule, to restore a diverse microbiota. It is the standard of care for multiply recurrent CDI, with published cure rates above 90 per cent. Licensed oral products such as SER-109 (Vowst) and RBX2660 (Rebyota) are now available in some settings.

  • How is C. difficile spread stopped in hospital?

    Patients are nursed in a single room with contact precautions. Staff use PPE and wash hands with soap and water rather than alcohol gel, because alcohol does not kill the spores. Rooms and equipment are cleaned with a chlorine-based disinfectant, and every case is reported to UKHSA within 24 hours as part of national surveillance.

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