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Pseudomembranous colitis

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Clostridium difficile article more useful, or one of our other health articles.

Synonyms: Clostridium difficile-associated diarrhoea/disease, CD-positive diarrhoea, antibiotic-associated colitis

Pseudomembranous colitis (PMC) is an acute, exudative colitis usually caused by Clostridioides difficile (C. difficile - formerly Clostridium difficile). PMC can rarely be caused by other bacteria - eg, Staphylococcus spp. or enterotoxigenic Clostridium perfringens, Campylobacter spp., Listeria spp. and Salmonella spp.

PMC has emerged, particularly in recent years, as a major and very expensive healthcare problem. Spores formed by the organism are implicated in spread of infection and have implications for hygiene and prevention of infection. C. difficile is an anaerobic Gram-positive rod which secretes two types of toxin (A and B), which cause disruption to the barrier function of the colonic mucosa. They are cytotoxic to cells of the intestinal tract, B being about 1,000 times more potent than A. Transmission of infection is via an indirect faeco-oral route, through spores left on surfaces. The spores can survive for months and patients can become carriers. The risk of colonisation increases with length of hospital stay.

C. difficile is classified into strains by polymerase chain reaction (PCR) ribotyping:

  • Ribotype 001 is a common cause of C. difficile infection (CDI) in the UK.

  • C. difficile 027 (also known as C. difficile NAP1/027 or C. difficile BI/NAP1/027) is associated with higher mortality, severity and relapse rate.

  • C. difficile 078 has a higher incidence among community-acquired C. difficile infection (CA-CDI).

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  • The incidence of primary and recurrent CDI has increased around the world, even after considerable efforts in the last decade. Increase risk of primary CDI is due in part to increasing age of populations and increasing numbers of residents in long-term care facilities. Antibiotic overuse and the emergence of resistance to commonly-used antibiotics such as vancomycin are contributory factors to recurrent infections. Increased recognition and reporting of infections may however account for some of this apparent increase1 .

  • However, counts and rates for CDI are falling across the NHS. In England, while rates remained substantial, they were seen to taper between 2009 and 2016: NHS trusts in England reported an incidence of 24 cases per 100,000 population (13,286 cases) in the 2017/18 financial year, which decreased by 76.1% in a decade (100.3 cases per 100,000 population, 55,498 cases in 2007/08).

  • An American study found an incidence of 8.3 cases of hospital-associated CDI per 10 000 patient-days2 .

  • Any antibiotic can increase the risk of CDI, including metronidazole and vancomycin, which are used in the treatment of CDI3 .

  • Disease has been reported following as little as one dose of antibiotic.

  • Although the attributable risk has varied among studies, fluoroquinolones, macrolides, clindamycin, beta-lactam/beta-lactamase inhibitors and cephalosporins have been shown to pose a significant risk for the development of CDI4 .

  • Antineoplastic agents and proton pump inhibitors have also been associated with CDI5 .

Risk factors6

  • Prolonged courses of antibiotics.

  • Multiple antibiotic usage.

  • Increasing age.

  • Severe comorbidity.

  • Non-surgical invasive gastrointestinal procedures.

  • Presence of a nasogastric tube.

  • Inpatient residence on ITU.

  • Current use of proton pump inhibitors or H2 receptor antagonists.

  • Increasing duration of hospital stay; patients in long-term care facilities.

  • Immunocompromised patients.


Colonisation with C. difficile can be associated with a range of possible clinical states:

  • The asymptomatic carrier state.

  • Mild self-limited diarrhoea.

  • Pseudomembranous colitis.

  • Fulminant colitis.

Generally there is a history of antibiotic exposure together with risk factors for colonisation.

  • Typically, symptoms come on between 5 and 10 days after antibiotic therapy. Occasionally patients will not have had antibiotic exposure.

  • Most patients become unwell during their course of antibiotics, but 25-40% may not do so for as many as 10 weeks afterwards7 .

  • Most affected individuals experience watery diarrhoea (varies from self-limiting to severe and debilitating) ± blood-stained stools, abdominal cramps, fever (especially so in severe cases), rigors ± sepsis.

  • Severe abdominal pain is uncommon but may mimic an acute abdomen.

  • Frank rectal bleeding suggests other causes (for example, inflammatory bowel disease).

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Differential diagnosis


  • FBC (WCC elevated in 80%, often very high).

  • Renal function tests and electrolytes.

  • Hypoalbuminaemia may be present (due to a protein-losing enteropathy).

  • Diagnosis in CDI and PMC focuses on detection either of C. difficile or of its toxins in stool samples. The particular method used and the number of samples required will depend on the laboratory. Public Health England (PHE) advises sending one sample, and has an algorithm which dictates whether further testing is necessary. Samples can usually be frozen or refrigerated if more than a four-hour delay in processing is expected. Liaison with the laboratory may be helpful to avoid delay. Methods of testing by NHS laboratories include toxin enzyme immunoassays (EIAs), toxin gene (NAAT or PCR) and glutamate dehydrogenase (GDH) EIA,

  • Testing for C. difficile or its toxins should be performed only on diarrhoeal (unformed) stool, unless ileus due to C. difficile is suspected. Testing of stool from asymptomatic patients is not clinically useful9 .

  • Sigmoidoscopy (or colonoscopy):

    • Can show the characteristic pseudomembranous plaque appearance in about half of affected patients.

    • May require biopsy to confirm diagnosis.

    • Is not used routinely but is usually performed if rapid diagnosis is needed or in a patient who has ileus (often as part of work-up for other colonic disease).

  • Imaging studies:

    • Plain X-rays and CT scanning may be helpful.

    • Useful in severe disease but not likely to be helpful in early or mild colitis.

    • Can detect complications (perforation, toxic dilatation).

    • Barium enemas can be harmful and should be avoided.

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Any of the following defines a C. difficile infection case in patients aged 2 years and above and must be reported to PHE or the equivalent agency in Northern Ireland, Scotland and Wales8 .

  • Diarrhoeal stools where the specimen is C. difficile toxin-positive.

  • Toxic megacolon or ileotomy where the specimen is C. difficile toxin-positive.

  • PMC revealed by lower gastrointestinal endoscopy or computerised tomography.

  • Colonic histopathology characteristic of CDI (with or without diarrhoea or toxin detection) on a specimen obtained during endoscopy or colectomy.

  • Faecal specimens collected post-mortem where the specimen is C. difficile toxin-positive or tissue specimens collected post-mortem where pseudomembranous colitis is revealed or colonic histopathology is characteristic of CDI.


  • Correct fluid losses or electrolyte imbalance with oral or intravenous (IV) electrolyte solutions.

  • Avoid antiperistaltic agents such as loperamide or opiates (codeine) because of the risk of retention of toxins in the lumen.

  • Ceasing the causative antibiotic (if possible) allows resolution in ~3 days in 22%. Consider changing to an antibiotic less likely to cause PMC - aminoglycosides, macrolides, vancomycin or tetracyclines.

  • Adherence to the recommended infection control measures and the judicious use of antibiotics should also be part of the global management of CDI in long-term care facilities10 .

Choice of antibiotic

The National Institute for Health and Care Excellence (NICE) recommends the following antibiotics for adults aged 18 years and over11 :


Antibiotic, dosage and course length

First-line antibiotic for a first episode of mild, moderate or severe C. difficile infection

Vancomycin: 125 mg orally four times a day for 10 days

Second-line antibiotic for a first episode of mild, moderate or severe C. difficile infection if vancomycin is ineffective

Fidaxomicin: 200 mg orally twice a day for 10 days

Antibiotics for C. difficile infection if first- and second-line antibiotics are ineffective

Seek specialist advice. Specialists may initially offer:

Vancomycin: up to 500 mg orally four times a day for 10 days

With or without Metronidazole: 500 mg intravenously three times a day for 10 days

Antibiotic for a further episode of C. difficile infection within 12 weeks of symptom resolution (relapse)

Fidaxomicin: 200 mg orally twice a day for 10 days

Antibiotics for a further episode of C. difficile infection more than 12 weeks after symptom resolution (recurrence)

Vancomycin: 125 mg orally four times a day for 10 days


Fidaxomicin: 200 mg orally twice a day for 10 days

Antibiotics for life-threatening C. difficile infection

Seek urgent specialist advice, which may include surgery. Antibiotics that specialists may initially offer are:

Vancomycin: 500 mg orally four times a day for 10 days

With Metronidazole: 500 mg intravenously three times a day for 10 days

There is insufficient evidence of any benefit with probiotic therapy as an adjunct to antibiotic therapy for C. difficile colitis. There is no evidence to support the use of probiotics alone in the treatment of C. difficile colitis12 .

  • Use clinical judgement to decide whether vancomycin has worked, but wait seven days before making this decision.

  • Check with the British National Formulary (BNF) for contra-indications and special populations - eg, patients with hepatic or renal failure13 .

  • Children can be treated as for adults, but check the BNF for Children (BNFC) for dosages, licensed indications and available preparations14 .


  • Surgery may be life-saving for patients with acute severe colitis.

  • Referral for a surgical opinion is required if the patient fails to respond to treatment or has signs of an acute abdomen, radiological signs of acute disease, a rising white blood cell count, a rising creatinine concentration, or a rising lactate concentration.

NICE criteria for a diagnosis of severe colitis11 :

A white cell count greater than 15 x 09 per litre, or an acutely increased serum creatinine concentration (greater than 50% increase above baseline), or a temperature higher than 38.5°C, or evidence of severe colitis (abdominal or radiological signs). The number of stools may be a less reliable indicator of severity.


  • In healthy individuals a good response to treatment is usually expected but the illness can cause severe debility and prolonged hospital stays.

  • CDI is implicated as a significant cause of morbidity and mortality among hospitalised patients7 .

  • Recurrent colitis and diarrhoea occur in approximately 25% of patients7 .

  • Early identification of CDI and prompt initiation of therapy with the most appropriate agent are critical to minimise morbidity and mortality10 .


Complications of severe C. difficile colitis include dehydration, electrolyte disturbances, hypoalbuminaemia, toxic megacolon, bowel perforation, hypotension, acute kidney injury, systemic inflammatory response syndrome, sepsis and death9 . Extraintestinal manifestations are rare and include7 :

  • Bacteraemia.

  • Splenic abscess.

  • Osteomyelitis.

  • Reactive arthritis or tenosynovitis.


  • Administration of currently available probiotics is not recommended to prevent primary CDI, as there are limited data to support this approach.

  • Overall preventative measures, such as strict handwashing and patient isolation policies for patients with diarrhoea, seem to be effective. There is less evidence of benefit for environmental cleansing measures.

  • Handwashing should be done correctly to be effective. Alcohol gels do not kill spores and are not recommended16 .

  • Appropriate antibiotic prescribing; minimise the frequency and duration of antimicrobial therapy and the number of antimicrobial agents prescribed17 .

Further reading and references

  • Smith AB, Soto Ocana J, Zackular JP; From Nursery to Nursing Home: Emerging Concepts in Clostridioides difficile Pathogenesis. Infect Immun. 2020 Jun 22;88(7). pii: IAI.00934-19. doi: 10.1128/IAI.00934-19. Print 2020 Jun 22.
  1. Finn E, Andersson FL, Madin-Warburton M; Burden of Clostridioides difficile infection (CDI) - a systematic review of the epidemiology of primary and recurrent CDI. BMC Infect Dis. 2021 May 19;21(1):456. doi: 10.1186/s12879-021-06147-y.
  2. Marra AR, Perencevich EN, Nelson RE, et al; Incidence and Outcomes Associated With Clostridium difficile Infections: A Systematic Review and Meta-analysis. JAMA Netw Open. 2020 Jan 3;3(1):e1917597. doi: 10.1001/jamanetworkopen.2019.17597.
  3. Smits WK, Lyras D, Lacy DB, et al; Clostridium difficile infection. Nat Rev Dis Primers. 2016 Apr 7;2:16020. doi: 10.1038/nrdp.2016.20.
  4. Brown KA, Khanafer N, Daneman N, et al; Meta-analysis of antibiotics and the risk of community-associated Clostridium difficile infection. Antimicrob Agents Chemother. 2013 May;57(5):2326-32. doi: 10.1128/AAC.02176-12. Epub 2013 Mar 11.
  5. Tleyjeh IM, Bin Abdulhak AA, Riaz M, et al; Association between proton pump inhibitor therapy and clostridium difficile infection: a contemporary systematic review and meta-analysis. PLoS One. 2012;7(12):e50836. doi: 10.1371/journal.pone.0050836. Epub 2012 Dec 7.
  6. Diarrhoea - antibiotic associated; NICE CKS, July 2021 (UK access only)
  7. Clostridioides difficile: guidance, data and analysis; Public Health England
  8. Updated Guidance on the Diagnosis and Reporting of Clostridium Difficile; Dept of Health, March 2012
  9. Cohen SH, Gerding DN, Johnson S, et al; Clinical practice guidelines for Clostridium difficile infection in adults: 2010. Infect Control Hosp Epidemiol. 2010 May;31(5):431-55.
  10. Makris AT, Gelone S; Clostridium difficile in the long-term care setting. J Am Med Dir Assoc. 2007 Jun;8(5):290-9.
  11. Clostridioides difficile infection: antimicrobial prescribing; NICE Guidance (July 2021)
  12. Pillai A, Nelson R; Probiotics for treatment of Clostridium difficile-associated colitis in adults. Cochrane Database Syst Rev. 2008 Jan 23;(1):CD004611.
  13. British National Formulary (BNF); NICE Evidence Services (UK access only)
  14. British National Formulary for Children; NICE Evidence Services (UK access only)
  15. Noblett SE, Welfare M, Seymour K; The role of surgery in Clostridium difficile colitis. BMJ. 2009 May 6;338:b1563. doi: 10.1136/bmj.b1563.
  16. Jabbar U, Leischner J, Kasper D, et al; Effectiveness of alcohol-based hand rubs for removal of Clostridium difficile spores from hands. Infect Control Hosp Epidemiol. 2010 Jun;31(6):565-70. doi: 10.1086/652772.
  17. Antimicrobial stewardship: systems and processes for effective antimicrobial medicine use; NICE Guidelines (August 2015)

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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