FAQs for Clinicians about C. diff

What is C. diff?

C. diff is a spore-forming, Gram-positive anaerobic bacillus that produces two exotoxins: toxin A and toxin B. It is a common cause of antibiotic-associated diarrhea (AAD). It accounts for 15 to 25% of all episodes of AAD.

What diseases result from C. diff infection (CDI)?

  • pseudomembranous colitis (PMC)
  • toxic megacolon
  • perforations of the colon
  • sepsis
  • death (rarely)

What are the main clinical symptoms?

  • watery diarrhea
  • fever
  • loss of appetite
  • nausea
  • abdominal pain/tenderness

Which patients are at increased risk for CDI?

The risk for disease increases in patients with:

  • antibiotic exposure (e.g., fluoroquinolones, third/fourth generation cephalosporins, clindamycin, carbapenems)
  • gastrointestinal surgery/manipulation
  • long length of stay in healthcare settings
  • a serious underlying illness
  • immunocompromising conditions
  • advanced age
  • other possible causes include Proton pump inhibitors, H2-blockers

What are the differences between colonization and infection?

Colonization is more common than CDI. The patient exhibits NO clinical symptoms (asymptomatic) but does test positive for the C. diff organism or its toxin.

With infection, the patient exhibits clinical symptoms and tests positive for the C. diff organism or its toxin.

Which laboratory tests are commonly used for diagnosis?

  • Molecular tests: FDA-approved PCR assays, which test for the gene encoding toxin B, are same-day tests that are highly sensitive and specific for the presence of a toxin-producing C. diff organism. Molecular assays can be positive for C. diff in individuals who are asymptomatic. When using multi-pathogen (multiplex) molecular methods, the results should be read with caution. In addition, patients with other causes of diarrhea might be positive, which could lead to over-diagnosis and treatment.
  • Antigen detection for C. diff: These are rapid tests (<1 hour) that detect the presence of C. diff antigen. Because results of antigen testing alone are nonspecific, antigen assays have been employed in combination with tests for toxin detection, PCR, or toxigenic culture in two-step testing algorithms.ve results occur when specimens are not promptly tested or kept refrigerated until testing can be done.
  • Toxin testing for C. diff:
    • Tissue culture cytotoxicity assay detects toxin B only. This assay requires technical expertise to perform, is costly, and requires 24 to 48 hours for a final result. It does provide specific and sensitive results for CDI. While it served as a historical gold standard for diagnosing clinical significant disease caused by C. diff, it is recognized as less sensitive than PCR or toxigenic culture for detecting the organism in patients with diarrhea.
    • Enzyme immunoassay detects toxin A, toxin B, or both A and B. Due to concerns over toxin A-negative, B-positive strains causing disease, most laboratories employ a toxin B-only or A and B assay. Because these are same-day assays that are relatively inexpensive and easy to perform, they are popular with clinical laboratories. However, there are increasing concerns about their relative insensitivity (less than tissue culture cytotoxicity and much less than PCR or toxigenic culture).
    • C. diff toxin is very unstable. The toxin degrades at room temperature and might be undetectable within two hours after collection of a stool specimen. False-negati

Detecting Patients at Increased Risk

  • Stool culture for C. diff: While this is the most sensitive test available, it is the one most often associated with false-positive results due to the presence of nontoxigenic C. diff strains. However, this can be overcome by testing isolates for toxin production (i.e. so-called “toxigenic culture”). Nonetheless, stool cultures for C. diff are labor-intensive, require an appropriate culture environment to grow anaerobic microorganisms, and have a relatively slow turnaround time (i.e. results available in 48 to 96 hours), making them less clinically useful overall. Results of toxigenic cultures do serve as a gold standard against which other test modalities are compared in clinical trials of performance.

How is C. diff transmitted?

C. diff is shed in feces. Any surface, device, or material (such as commodes, bathtubs, and electronic rectal thermometers) that becomes contaminated with feces could serve as a reservoir for the C. diff spores. C. diff spores can also be transferred to patients mainly via the hands of healthcare personnel who have touched a contaminated surface or item.

How is CDI treated?

In about 20% of patients, CDI will resolve within two to three days of discontinuing the antibiotic to which the patient was previously exposed. The infection can usually be treated with an appropriate course (about 10 days) of antibiotics, including oral vancomycin or fidaxomicin. After treatment, repeat C. diff testing is not recommended if the patient’s symptoms have resolved, as patients often remain colonized.

What are the steps to prevent spread?

If a patient has had ≥ 3 stools in 24 hours:

  • Order a C. diff test if other etiologies of diarrhea are ruled out.
  • Isolate patients with C. diff immediately, even if you only suspect CDI.
  • Wear gloves and gowns when treating patients with C. diff, even during short visits. Gloves are important because hand sanitizer doesn’t kill C. diff and handwashing might not be sufficient alone.
  • In patient being evaluated for C. diff, reassess correctness of antibiotics.

If the patient is positive for CDI:

  • Continue isolation and contact precautions.
  • Use antibiotics judiciously.
  • Clean room surfaces thoroughly on a daily basis while treating a patient with C. diff and upon patient discharge or transfer using an EPA-approved spore-killing disinfectant.
  • When a patient transfers, notify the new facility if the patient has or had a C. diff infection.

CDIs can be prevented by using infection control recommendations and more careful antibiotic use.

How can CDIs be prevented in hospitals and other healthcare settings?

  • Use antibiotics judiciously.
  • Use contact precautions for patients with known or suspected CDI:
    • Place these patients in private rooms. If private rooms are not available, they can be placed in rooms (cohorted) with other CDI patients.
    • Use gloves when entering patients’ rooms and during patient care.
    • Perform hand hygiene after removing gloves.
      • Because alcohol does not kill C. diff spores, use of soap and water is more effective than alcohol-based hand rubs. However, early experimental data suggest that, even using soap and water, the removal of C. diff spores is more challenging than the removal or inactivation of other common pathogens.
  • Using gloves to prevent hand contamination remains the cornerstone for preventing C. diff transmission via the hands of healthcare personnel; any theoretical benefit from instituting soap and water must be balanced against the potential for decreased compliance resulting from a more complex hand hygiene message.
  • If your institution experiences an outbreak, consider using only soap and water for hand hygiene after removing gloves while caring for patients with CDI.
  • Use gowns when entering patients’ rooms and during patient care.
  • Dedicate or perform cleaning of any shared medical equipment.
  • Continue these precautions until diarrhea ceases.
    • Because C. diff-infected patients continue to shed the organism for a number of days following cessation of diarrhea, some institutions routinely continue isolation and contact precautions for either several days beyond symptom resolution or until discharge, depending upon the type of setting and average length of stay.
  • Implement an environmental cleaning and disinfection strategy.
    • Ensure adequate cleaning and disinfection of environmental surfaces and reusable devices, especially items likely to be contaminated with feces and surfaces that are touched frequently.
      • Ensure daily and terminal cleaning of patient rooms.
    • Use an Environmental Protection Agency (EPA)-registered disinfectant with a sporicidal claim for environmental surface disinfection after cleaning in accordance with label instructions. (Note: Only hospital surface disinfectants listed on EPA’s List KExternal are registered as effective against C. diff spores.)
    • Follow the manufacturer’s instructions for disinfection of endoscopes and other devices.

Recommended infection control practices in long-term care and home health settings are similar to those practices taken in traditional healthcare settings.

What can I use to clean and disinfect surfaces and devices?

Surfaces should be kept clean, and body substance spills should be managed promptly, as outlined in CDC’s Guidelines for Environmental Infection Control in Health-Care Facilities. Routine cleaning should be performed prior to disinfection. EPA-registered disinfectants with a sporicidal claim have been used with success for environmental surface disinfection in those patient-care areas where surveillance and epidemiology indicate ongoing transmission of C. diff.

Note: EPA-registered disinfectants (List K) are recommended for use in patient-care areas. When choosing a disinfectant, check product labels for inactivation claims, indications for use, and instructions.

How have CDIs changed?

After tremendous increases during 2000 and 2011, CDI rates have plateaued at historic highs and have shown some decline. In 2011, an estimated 450,000 CDIs in the United States were reported with an estimated 29,300 associated deaths; C. diff accounted for 12.1% of all healthcare-associated infections. An epidemic strain, ribotype 027 (formerly referred to as NAP1/BI/027), which emerged in the mid-2000s, resulted in severe outbreaks across many countries. This strain was more virulent, possibly due to its increased production of toxins A and B and its production of an additional toxin known as binary toxin. In addition, it is more resistant to a commonly used class of antimicrobials known as the fluoroquinolones. With concomitant reduction in fluoroquinolones, the prevalence of ribotype 027 has reduced but continues to remain the major ribotype in the United States. Clinicians should be aware of the recent emergence of ribotype 078 in Netherlands, which affects a younger population and is seen more in the community.

What should healthcare facilities do in response to increased rates or the emergence of a new strain?

Healthcare facilities should monitor the number of CDIs and, especially if rates at the facility increase, the severity of disease and patient outcomes. If an increase in rates or severity is observed, healthcare facilities should contact their health departments. Reporting cases to NHSN is important for helping healthcare facilities track their progress in preventing CDI and understand their performance in relation to national goals and both state and national prevention progress.

Healthcare facilities should reassess compliance with core recommended practices, including infection control, environmental cleaning (Options for Evaluation of Environmental Cleaning), and antibiotic stewardship for known cases of CDI.

If compliance with core recommendations appears high, consideration should be made to implement supplemental recommendations as described in the toolkit. If assistance is needed with these measures, additional help should be sought from local or state health departments or local infection control experts.