Microbe of the Month: Clostridium difficile

Clostridium difficile 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) and accounts for 15 percent to 25 percent of all episodes of AAD.

C. difficile is shed in feces. Any surface, device, or material (e.g., commodes, bathing tubs, and electronic rectal thermometers) that becomes contaminated with feces may serve as a reservoir for the C. difficile spores. C. difficile spores are transferred to patients mainly via the hands of healthcare personnel who have touched a contaminated surface or item.

C. difficile causes diarrhea and more serious intestinal conditions such as pseudomembranous colitis (PMC), toxic megacolon, perforations of the colon, sepsis and in some cases, death. The symptoms of C. difficile disease include watery diarrhea, fever, loss of appetite, nausea and abdominal pain/ tenderness.

An individual is considered to be colonized with C. difficile if the patient exhibits no clinical symptoms; tests positive for C. difficile organism and/or its toxin more common than C. difficile-associated disease; and has C. difficileassociated disease. An individual is considered to be infected with C. difficile if he or she exhibits clinical symptoms the patient tests positive for the C. difficile organism and/or its toxin.

There are several laboratory tests used to diagnose C. difficile-associated disease. Stool culture for C. difficile is the most sensitive test available, but the one most often associated with false-positive results due to presence of non-toxigenic strains. Stool cultures for C. difficile also are labor intensive and require the appropriate culture environment to grow anaerobic microorganisms. Results are available within 48 to 96 hours of the test. Antigen detection for C. difficile involves rapid tests (less than an hour) that detect the presence of C. difficile antigen by latex agglutination or immunochromatographic assays. They must be combined with toxin testing to verify diagnosis. Enzyme immunoassay detects toxin A, toxin B, or both A and B. It is a same-day assay but less sensitive than the tissue culture cytotoxicity assay. 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 C. difficile-associated disease. C. difficile toxin is very unstable. The toxin degrades at room temperature and may be undetectable within two hours after collection of a stool specimen. False-negative results occur when specimens are not promptly tested or kept refrigerated until testing can be done.

In approximately one-quarter of patients, C. difficile-associated disease 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 metronidazole or vancomycin (administered orally). After treatment, repeat C. difficile testing is not recommended if the patients symptoms have resolved, as patients may remain colonized.

C. difficile-associated disease can be prevented in healthcare settings by taking the following actions:

Use antibiotics judiciously Use Contact Precautions:

For patients with known or suspected C. difficile-associated disease:

• Place these patients in private rooms. If private rooms are not available, these patients can be cohorted) with other patients with C. difficile-associated disease.

• Perform hand hygiene using either 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-associated disease; alcohol-based hand rubs may not be as effective against spore-forming bacteria.

• Use gloves when entering patients rooms and during patient care.

• Use gowns if soiling of clothes is likely.

• Dedicate equipment whenever possible. Note: Continue these precautions until diarrhea ceases. 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.

• Use an Environmental Protection Agency (EPA)-registered hypochlorite-based disinfectant for environmental surface disinfection after cleaning in accordance with label instructions. Generic sources of hypochlorite (e.g., household chlorine bleach) also may be appropriately diluted and used. (Note: alcohol-based disinfectants are not effective against C. difficile and should not be used to disinfect environmental surfaces.)

• Follow the manufacturers instructions for disinfection of endoscopes and other devices

• Surfaces should be kept clean, and body substance spills should be managed promptly as outlined in CDCs Guidelines for Environmental Infection Control in Health-Care Facilities. Hospital cleaning products can be used for routine cleaning. Hypochlorite-based disinfectants have been used with some success for environmental surface disinfection in those patient-care areas where surveillance and epidemiology indicate ongoing transmission of C. difficile. Consult the aforementioned guidelines for use conditions for generic sources of hypochlorite-based products (e.g., household chlorine bleach) for disinfection of environmental surfaces.

Source: CDC

Recommended reading

• In May 2006, the FDA, the CDC and the NIH held a joint workshop on emerging clostridial diseases. A transcript of the proceedings can be accessed at www.fda.gov/cder/meeting/clostridial/transcript.pdf

• Boone N, Eagan JA, Gillern P, Armstrong D, Sepkowitz KA. Evaluation of an interdisciplinary re-isolation policy for patients with previous Clostridium difficile diarrhea. Am J Infect Control 1998;26:5847.

• CDC. Guidelines for environmental infection control in health-care facilities. MMWR 2003;52 (RR10):142.