C. difficile

Figure: C. difficile bacteria forming spores on a stainless-steel surfaceFOR YEARS Clostridium difficile infection, which is often associated with antibiotic therapy, has been a common cause of health-care-associated diarrhea, particularly in elderly patients and long-term-care residents. Now a new, virulent strain of C. difficile– associated disease has emerged in the United States and Canada. Unlike the more familiar variety, it's not always associated with antibiotic use and may strike otherwise-healthy people in the community. This new C. difficile strain also produces more toxins and may be more resistant to fluoroquinolone antibiotics. In December 2005, the Centers for Disease Control and Prevention (CDC) published a report on severe C. difficile–associated disease (CDAD) in previously healthy people living in the community, including peripartum women. The report highlighted two patients—a pregnant woman and a 10-year-old girl—who lacked traditional risk factors for CDAD, such as recent antibiotic exposure, advanced age, hospitalization, or poor health. According to the CDC, community-associated and peripartum CDAD may be associated with close contact transmission, a high recurrence rate, young patient age, bloody diarrhea, and lack of antimicrobial exposure. None of the commonly available diagnostic tests differentiates among C. difficile strains, but most preventive and care recommendations are the same for all strains. In this article, I'll review what you need to know about this stubborn and dangerous pathogen, including how to support a patient with C. difficile–associated disease. Two tough toxins A Gram-positive anaerobic bacillus, C. difficile produces two exotoxins (toxin A and toxin B) that cause disease in humans. In its vegetative state, C. difficile has the capacity to form spores and can persist in the environment indefinitely. A person carrying C. difficile sheds the bacteria in feces. The bacteria are transmitted when someone touches a contaminated material or surface. (See How C. difficile gets around.) A patient is considered colonized with C. difficile if he tests positive for the pathogen or its toxin but exhibits no signs and symptoms (watery stools, fever, loss of appetite, nausea, and abdominal pain or tenderness). If a colonized patient is subsequently treated with an antibiotic, his normal bowel flora is altered, creating a favorable environment for C. difficile to multiply and release toxins. Antibiotics associated with a higher risk of C. difficile–associated disease include clindamycin, cephalosporins, and fluoroquinolones. A patient is diagnosed with CDAD if he tests positive for C. difficile and also exhibits signs and symptoms of infection. Diarrhea associated with CDAD is defined as three or more liquid stools per day for 2 or more days. The toxins produced by C. difficile cause colonic dysfunction and cell death. Besides severe diarrhea, potentially fatal clinical manifestations include pseudomembranous colitis, toxic megacolon, colonic perforation, sepsis, and ileus. Cultures and other tests Several lab tests can identify C. difficile. The health care provider may order a culture of a watery or loose stool specimen; this is the most sensitive test available. Antigen detection for C. difficile must be combined with toxin testing to verify diagnosis. The most frequently utilized test is an enzyme immunoassay to detect toxin A, toxin B, or both A and B. It's less sensitive than a stool culture, partly because the toxins are unstable at room temperature. Make sure specimens are transported to the lab immediately after collection because toxins may be undetectable in 2 hours. Other lab tests that may aid in the diagnosis of C. difficile are a polymerase chain reaction test and histopathologic examination, which can reveal megacolon and pseudomembranous colitis. Colonoscopy may help diagnose pseudomembranous colitis. Treating CDAD If the patient has antibiotic-associated CDAD, the antibiotic should be discontinued if possible. In about 25% of cases, symptoms resolve within 3 days of discontinuing the offending antibiotic. A 10- to 14-day course of treatment with metronidazole is currently recommended as first-line therapy for CDAD, although some reports suggest the new C. difficile strain may be resistant to this drug. Oral vancomycin is recommended if the patient doesn't respond to metronidazole. Those with refractory CDAD may respond to one of these therapies: vancomycin plus cholestyramine vancomycin enema reestablishment of normal colonic flora with vancomycin followed by a synthetic fecal bacterial enema administration of a nontoxigenic C. difficile strain to compete with the toxigenic strain. Surgery is indicated if the patient doesn't respond to antibiotic treatment and if toxic megacolon or colonic perforation is suspected. Caring for hospitalized patients To prevent the transmission of C. difficile, follow contact precautions according to your health care facility's policies and procedures and CDC guidelines. Patients with known or suspected CDAD should be placed in a private room or in a room with another patient with CDAD. Wear gloves when entering the patient's room and during patient care. If contamination of your clothing is likely, wear a gown as well. Perform hand hygiene after glove removal. Because alcohol-based hand hygiene products are ineffective against C. difficile spores, follow policies and procedures for washing hands with soap and water when caring for patients identified with C. difficile. Monitor your patient for signs and symptoms of fluid and electrolyte imbalances and administer I.V. fluids to replace fluids and electrolytes if ordered. Don't administer an antiperistaltic drug such as Lomotil (diphenoxylate and atropine) to a patient with CDAD because it may predispose her to toxic megacolon. Provide meticulous skin care to prevent skin breakdown and teach the patient and family to perform hand hygiene with soap and water. Teach all patients undergoing antibiotic therapy to report fever, abdominal pain, or diarrhea to their health care provider. Stopping the spread Dedicate medical equipment such as blood pressure cuffs and thermometers to patients with CDAD whenever possible. Medical devices that can't be dedicated to the patient (for example, ultrasound equipment or a blood glucose meter) should be wiped down with a disinfectant before use on another patient. Because direct exposure to contaminated patient-care items and surfaces in patients' rooms spreads infection, environmental cleaning and disinfection is essential. Ordinary hospital cleaning products can be used for routine cleaning and disinfection, but in situations where C. difficile transmission is occurring, the CDC recommends using hypochlorite-based disinfectants. C. difficile gets around Because Clostridium difficile is found in feces, it can be transmitted when a person touches a surface contaminated with feces, then touches her mouth or other mucous membranes (direct transmission). Indirect transmission occurs when a health care provider spreads the bacteria through hand contact from one patient to another patient or contaminates a surface that's then touched by a patient or health care worker. Medical equipment and surfaces contaminated with feces, such as commodes and electronic rectal thermometers, can be reservoirs for the C. difficile spore. SELECTED WEB SITES Centers for Disease Control and Prevention: Information about a new strain of Clostridium difficile http://www.cdc.gov/ncidod/dhqp/id_CdiffFAQ_newstrain.html#1 Clostridium difficile infections http://www.cdc.gov/ncidod/dhqp/id_Cdiff.html Last accessed on July 10, 2006. Shannon Oriola is lead infection control practitioner at Sharp Metropolitan Medical Campus in San Diego, Calif.

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