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Information about the Current Strain of Clostridium difficile

Updated 2010

How has Clostridium difficile (C. difficile) infections (CDI) changed?

Over the past several years nationwide, states have reported increased rates of C. difficile infection, noting more severe disease and an associated increase in mortality. C. diff infection remains a disease mostly associated with healthcare (at least 80%) Patients most at risk remain the elderly, especially those using antibiotics. Although the elderly are still most affected, more disease has been reported in traditionally ‘low risk’ persons such as healthy person in the community, and peripartum women.

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What are the possible reasons for this change in the disease?

The increased rates and/or severity of disease may be caused by changes in antibiotic use, changes in infection control practices, or the emergence of the epidemic strain of C. diff infection with increased virulence and/or antimicrobial resistance.

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Has a new strain of C. difficile been identified?

Yes, in 2004 the emergence of a new epidemic strain of C. difficile-associated disease causing hospital outbreaks in several states was reported by the Centers for Disease Control and Prevention (CDC) at scientific meetings.

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What is unique about this epidemic strain?

The epidemic strain, identified in 2004 appears to be more virulent, with ability to produce greater quantities of toxins A and B. In addition, it is more resistant to the antibiotic group known as floroquinolones.

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How is the epidemic strain detected?

Like other strains of C. difficile, this new strain can be detected in the stool of infected patients by using laboratory tests that are commonly available in most hospitals. However, none of the FDA-approved tests differentiate between the various strains of C. difficile. Fortunately, because the control measures for outbreaks of any strain of C. difficile are similar, identification of the specific strain is not imperative for controlling outbreaks.

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Is treatment of this new strain different?

The usual treatment for C. difficile infection includes, if possible, stopping antibiotics being given for other purposes and/or treatment with metronidazole or vancomycin. In order to reduce selective pressure for vancomycin resistance in enterococci, current guidelines recommend the first-line use of metronidazole over vancomycin.

However, recent reports suggest that the new strain may not respond as well to treatment with metronidazole despite the absence of laboratory evidence of metronidazole resistance. This may be due to increased virulence in the new strain. Depending upon the severity of the C. diff infection, metronidazole is likely to be the appropriate first-line therapy for most cases. Regardless of what therapy is used, patients should be carefully monitored to be sure they are responding to therapy and that there is no deterioration in their condition. (Link to IDSA guidelines on internet)

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How does fluoroquinolone resistance affect management of this strain?

Increased fluoroquinolone resistance does not affect the management of infections caused by this strain. Fluoroquinolones have never been recommended for treatment of C. difficile infection and susceptibility testing is performed only as a part of an epidemiological investigation. However, resistance to fluoroquinolones may provide the new strain with an advantage over susceptible strains to spread within healthcare facilities where these antibiotics are commonly used.

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What should healthcare facilities do in response to the emergence of the new strain?

Healthcare facilities should monitor the number of C. difficile infections 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 reassess compliance with the recommended infection control measures for known cases of C. diff infection including the following:

  • Perform hand hygiene using an alcohol-based hand rub or soap and water.
    • If your institution experiences an outbreak, consider using only soap and water for hand hygiene when caring for patients with C. difficile infection; alcohol-based hand rubs may not be as effective against spore-forming bacteria.
  • Contact precautions
  • Environmental cleaning and disinfection strategies.

If compliance is optimal with continued increase in rates and disease severity, review antimicrobial use to determine whether particular antimicrobials are associated with cases of C. diff infection. If assistance is needed with these measures, additional help should be sought from local or state health departments and/or local infection control experts.

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