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Clostridium difficile Infection (CDI) Outbreaks in Public Hospitals

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Reporting Obligations

Outbreaks of Clostridium difficile infection (CDI) in public hospitals shall be reported immediately by phone to the local Health Unit.


Aetiologic Agent

Clostridium difficile is a Gram-positive, spore-forming, anaerobic bacillus. It is widely distributed in the environment and colonizes up to 3–5% of adults without causing symptoms. Some strains can produce two toxins that are responsible for diarrhea: toxin A and toxin B.

Clinical Presentation

Symptoms of CDI include:

  • Diarrhea, defined as: loose/watery bowel movements (conform to the shape of the container), and the bowel movements are unusual or different for the patient, and there is no other recognized etiology for the diarrhea (i.e. laxative use)
  • Fever
  • Loss of appetite
  • Nausea and
  • Abdominal pain or tenderness

Complications include dehydration and colitis and may also lead to life threatening systemic toxicity requiring surgical intervention and may also lead to death. Recurrence of CDI is common and occurs in about 30% of cases.

Modes of Transmission

C. difficile is widely distributed in the environment. It produces spores that survive for longer periods of time and are resistant to destruction by environmental factors (e.g. temperature, humidity), including standard cleaning agents. In an effort to protect itself from undesirable environmental conditions, it assumes its spore form.

C. difficile is spread through the fecal-oral route of transmission. C. difficile can be acquired in both hospital and community settings. C. difficile can be transmitted and/or acquired by patients through contact with contaminated surfaces (including both vegetative cells and spores).

CDI may occur when antibiotics kill normal bowel bacteria and allow the C. difficile to grow. When C. difficile grows, it may produce toxins, which can damage the bowel and may cause diarrhea.

Incubation Period

The incubation period of C. difficile following acquisition has not been clearly defined. Studies have determined that onset of infection can occur within 48 hours after exposure and up to 3 months post exposure.

Period of Communicability

Precise period of communicability is unknown; it may vary depending on the amount of toxin in the stool, which can vary from very small to large spores and are very difficult to eliminate from surfaces and objects. Cytotoxins may persist in stool for weeks.

Risk Factors/Susceptibility

Risk Factors associated with CDI include:

  • a history of antibiotic usage, particularly broad spectrum antibiotics that affect the normal gut bacterial flora, such as fluoroquinolones
  • immunosuppressive therapy post-transplant
  • proton pump inhibitors
  • bowel disease and bowel surgery
  • chemotherapy
  • hospitalization

Additional risk factors that predispose some people to develop more severe disease include:

  • history of CDI
  • increased age
  • immunosuppressive therapy
  • recent surgery
  • CDI with the hypervirulent strain of C. difficile.

Diagnosis and Laboratory Testing

Following consultation between the institution and the Medical Officer of Health (or representative), decisions on the declaration of an outbreak will be made based on the following criteria:

  • Significant (as determined by the facility and health unit) increase in CDI numbers or rate compared to own baseline and/or that of comparator institutions
  • Recognized control measures are in place and are being used
  • Epidemiologic evidence of ongoing nosocomial transmission within the ward/unit or facility

Any of the following will constitute a confirmed case of CDI:

  • Diarrhea (defined as three or more episodes within a 24-hour period) with lab confirmation of toxin A or B for C. difficile
  • Visualization of pseudomembranes on sigmoidoscopy or colonoscopy
  • Histological/pathological diagnosis of pseudomembranous colitis
  • Diagnosis of toxic megacolon

Stool specimen collection should occur as soon as possible after the onset of symptoms. Specimens are not recommended from patients who are less than 12 months old. Formed stool specimens will be rejected.

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Treatment and Case Management

Treatment of individual cases will be under the direction of the attending physician.

For case and outbreak management, refer to the Provincial Infectious Diseases Advisory Committee, Annex C document “Testing, Surveillance and Management of Clostridium difficile in all Health Care Settings”. Outbreaks will be managed in consultation with the local Health Unit.

Patient Information

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Additional Resources

Health Canada, Public Health Agency of Canada. “It’s your health: C.difficile (Clostridium difficile)“.

Provincial Infectious Diseases Advisory Committee: Annex C: Testing Surveillance and Management of Clostridium difficile in all Health Care Settings”.


Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2022.